How

U just press on their username or profile PIC which takes u to their home page the follow button is very visible

go to the person you wanna follow's homepage just by clicking their pfp. scroll down then you'll see their bio(if they have one). there you'll also their pfp. under that, you'll see a "follow" button and a "send mail" button. juct click the "follow" button and you can even send a little message to the person you will be following. hope that helps!

Thnx