I want people to be able to come to my game and be able to listen to my Plug.dj from ROBLOX.?
Well you Really cant make an HTTPService. Its already on your Roblox games. So if you want to have people to come into your game and you want people to listen to something.. Your best bet would be to Look for an Gui Music Player. Then from there edit it to your Satisfaction.
I am not sure if using plug.dj on ROBLOX Is possible?
support.plug.dj/entries/30455216-Documentation?
That is the API Documentation, I am not sure if you could do it though but it could be possible ;)