You can unfollow a user directly from their user profile.
Access a user's profile by tapping their profile picture from their live stream, a direct message, or a user search.
From the user's profile, tap the pink following button.
You can also unfollow users from your own user profile.
Access your user profile from the bottom button panel.
Tap the "following" text beneath your username.
On the list of users that you follow, you will see a button to unfollow on the right side.
Tap the unfollow button to unfollow an individual user.