If you know someone’s Instagram handle, you can search for them by clicking on the magnifying glass at the bottom of the app.
You can actually search for specific accounts, hashtags, and places in this same spot.
As you spend time on Instagram, the app will get to know you. The search tab will be populated with suggested categories and posts that Instagram thinks you might enjoy. This is a great place to find new people or hashtags to follow!
To find friends you already know on Instagram, you will start by syncing up your phone’s contact list.
Instagram Tip: If your friend’s Instagram account is private, you may have to tap “Request” instead of “Follow,” so they can approve the connection.
Instagram Profile Screenshot: Android and iOS versions
In addition to tagging, you can also mention fellow Instagram users in the comments.
Technically, however, this is a mention, not a tag.
People you mention in comments will receive a notification, but these posts will not appear on their profile. (See the FAQs below for more information on where tagged photos appear.)
You can do mention people in comments on your own post, or on anyone’s post that has comments enabled, which most do.
Mentioning someone in a comment is a great way to share a post with a friend or co-worker to ensure it gets their attention.
To tag someone on Instagram comments:
Now let’s walk through that step-by-step process with pictures.
Begin by finding the post you want to comment on, then tap the comment icon:
Start typing your comment in the box that appears. When you are ready to tag, or mention, another user, type the @ symbol.
Next, begin typing the username of the person or business you want to mention. As you do, your Instagram friends with those letters in their username will appear in a drop-down menu. Tap the username you want to mention when it appears:
Finish writing your comment (don’t forget those emojis!) and then tap “Post.”
Once you’ve posted your comment, it will be available for anyone who follows that account to see.
People who have been mentioned in comments always appear in blue; just like hyperlinks on a website. And, just like a landing page, you can click on that blue username to view that account’s Instagram profile.
In August 2016, Instagram launched Instagram Stories, a social media experience similar to Snapchat with stories that appear on your profile and expire after 24 hours.
Here’s how to tag people on Instagram stories.
To create an Instagram story, go to your Instagram feed. (This is what appears when you log in, displaying the pictures from accounts you follow.)
From this screen, create an Instagram story by swiping right.
Use the white button in the center of the screen to take a picture, or hold it down to take a video. Swipe up to upload a picture or video from your camera roll.
Add any filters, text, or other effects. Then, to tag another Instagram user, tap the Instagram stickers icon.
The icon looks like a square smiley face with the corner folded over:
You’ll now see options for custom Instagram story stickers.
Tap the one that says “@mention.” This is how you will mention, or tag, another user in your Instagram story.
Begin typing the username of the person you want to tag.
As you do, Instagram will suggest friends who have usernames with the letters you are typing.
When the person you want to tag appears, tap on their profile picture. Their full username will then appear on your screen.
You have now tagged someone Instagram in your story. Before publishing, you may want to edit the sticker tag.
Now all that’s left to do is add the post to your story. Tap the “Your story” button in the lower-left corner to share with all of your followers, or “Close friends” to share your story with your share with story your Instagram close friends.
First we’ll start with the basics: How to tag someone when you are creating a new Instagram post.
Begin by opening your Instagram account.
Create a new post by clicking the “+” symbol in the bottom center of your screen.
More Instagram tips: Do more than share pictures; learn how to post on Instagram and create posts that perform.
Once you have selected your photo, click the word “Next” in the upper-right corner.
You are now on the Instagram Share screen. Add any desired comments, hashtags, or a location, then tap “Tag people.”
Your photo will now appear on a new screen. Tap where you want the tag to appear. For example, if you’re posting a picture of a group of friends, tap on a friend’s face to tag them.
In addition to friends and family, you can tag any brand who has an Instagram account. In this case, I am tagging an organization, so I am placing my tag where the company’s logo appears in the picture.
After tapping on the photo, the words “Who’s this” will appear where you’ve placed the tag. 
In the search bar at the top of your screen, search for the individual’s Instagram username.
Pro tip: Before you start tagging your Instagram photo, it’s helpful to know the correct spelling of the username.
The person’s username could appear automatically in the drop-down menu, or you may need to hit “enter” to see the search results.
Once you see the correct username, tap on it.
Follow steps five-to-seven again to tag more people in your post.
Once you’ve tagged someone (or multiple people) in your photo, save your changes.
On your Share screen, the “Tag People” row will display the usernames of anyone you have tagged.
Now all that’s left to do is hit the “Share” button and officially publish your post!