You can follow someone on Mastodon by clicking on the Follow button on their profile page. You can go to someone’s profile page by clicking on their name.
You can unfollow them by clicking the same button again. The button may have a different label after you’ve followed them (Unfollow, Following etc), but it will be in the same place on the screen.
I know someone has an account on Mastodon etc and I’ve tried searching for their account, but it doesn’t show up in the search results. How do I follow them?
If you’re trying to get someone’s profile page to appear and nothing else works, you can use their account address to make their profile appear. Copy and paste their account address into the search box, and this will force your server to show you their profile page.
If you don’t know their account address but you have some other means to communicate with them, try asking them directly. They can find their account address on their profile page, it’s just below their display name. There’s more info on the account addresses page.
If you’re just wanting to discover new accounts that you haven’t heard of before, use the suggestions on the account discovery page.