New to modding, can anyone help?

Morning all !

So I've acquired a chipped 360, no idea what chip is in it all I know is that it is capable of playing games downloaded from online and then burnt on to a disk!

I really want to learn how to Mod on GTAV and this is why I got the machine.

Could anyone out there point me in the right direction as to what to do next as I am a total NOOB to modding !!!

Thanks