First you should buy a domain name. You can do so at places like Go Daddy. Then you must somehow get the code for the game which then you can post on your site (schools block pages with ads so don't have ads).
Or simply get a free website. The domain name will be dumb, but it'll work if it's just for personal use. Google can probably find a few places where you can do so, or you could try webs.com
Then you must somehow get the code for the game which then you can post on your site
Im just going to point out those were all made by armor games paid developers.
If you want to get on armor games at school than try going to https://www.ranksz.armorbot.com/ which isn't blocked by my school. It will say that its an untrusted website when you try but Cormyn confirmed that armor games does own this website and its completely safe.