Doom modding

[I DUNNO LOL0329]

I want to make a doom mod but don't know how to make my own custom sprites over oringanl sprites and stuff I wanted to make a doom bible project pls help thanks

[Pencil of Doom]

Doom Bible? Look:http://forum.zdoom.org/viewtopic.php?f=19&t=52262&sid=e5a7d26b7caa983822c0616bcc43a95d