If you want to remove a user from your friends list, you must first go to the "Friends" section, by selecting the two-person profile icon, in the bottom right corner of your home screen. There you will find the user by their username or Facebook name and you will need to select their avatar/photo in order to go to their profile. Once you do, you will see the three dots icon in the top right corner and, if you click on it, you will see the option to unfollow them. This will remove the user from your friends list.
If the user is still on your friends list, we recommend that you force stop the application and then reopen it. This way, the user should no longer appear in your friends list.