More of just a question, but do I need to buy a website to use this?

Basically I tried to send an email and it said @proton.me domain is not supported yada yada register it at this link and I go to the link which was for the place where you got the API keys and it said I had to use a website I hosted for it, or did I misunderstand, sorry if bad I forgot a lot of the details and I’m on pain meds cuz I broke my wrist