How to tattoo with a homemade gun?

Same way as normal other than it wont look very good. You need to slow it down. That's all you need to do.

Without having even a vague idea of the exact mechanics of the tattoo machine you have made I can not give you any advice on how to use it.

The gun is either going too fast, too slow, too deep, to shallow, with the incorrect motion, at the wrong angle, without a tight enough focus area, with too much or too little force or one of several other problems.

i will try to be as nice as i can about this:

PLEASE STOP WHAT YOU'RE DOING

"homemade tattoo" is never a good idea, and you're endangering yourself and whoever else you're tattooing with your unsafe practices.

if you say you're a very good artist and love tattoo history, go get an apprenticeship from a reputable shop before you make any mistakes that are not so easy to fix.

You're asking us how to tattoo with the tattoo gun YOU made? Shouldn't you know how to use it since you made it?

Just buy a real one. http://tattookitscheap.com/