Muting and blocking are really important tools on Mastodon. They let you choose what you see and who you interact with.
To mute or block someone, go to one of their posts or their profile page and click ⋯, then select "Mute" or "Block".
Mutes hide someone from you without them knowing, whereas blocks totally cut off contact with an account and prevent interactions.
I've done a guide all about mutes and blocks on Mastodon which answers lots of questions:
