I don't know Weebly, but don't they have FTP-access...?
If yes, simply use a FTP program; I'd recommend the free open-source FileZilla.
1) Log on to your domain using the ftp credentials
2) Create a folder for your game
If, on the other hand, you DON'T have FTP access, then you have a problem. Then I'd recommend you to buy your own domain at a web hotel that gives you FTP-access.