How can I play these ROMs?
You need a flash cart. If you have a DSi, you need one that will work with the DSi. If you have a DS Lite or DS Phat, you can use an older and possibly cheaper flash cart. I suggest you check out http://gbatemp.net to learn more. With very few exception, all PMs to me asking for help with these ROMs will simply tell you to check out that site anyway.