Yes, of course you can add links. I often add a "reference" section at the bottom and put them there, but sometimes I just link in the body text, too.

Just be cautious, because Medium is strict about posts that look like advertising. If it's text links, that's fine. I once had a guy submit a post with actual "ads" that he'd made in canva and had to tell him it's probably a bit too overt. But simple links, that's fine!

Also, if you are using affiliate links (and you can) you'll also need to add a line at the bottom saying some of the links are affiliate links.

Sorry that was so long winded, but hope it was helpful. :)