You can find some really great tutorials on how to silk screen in book and on you tube. You have to buy a silk screening kit from a art supply store and get fabric specific ink.
Silk screening requires a bit of special equipment to do successfully. The equipment will cost several thousand dollars to set up to do your own sil screening.
One totally DIY way to do silk screen is to purchase a window screen, attach it to a frame, apply modge podge around the area you want the ink to go and smooth fabric paint over the screen with a flat spreader.
I use a website that sells you the shirts at low cost and then screens them before sending them to you. It's an easy way to costumize my own shirts without leaving my house.
Kits are available on the internet for single color silkscreening but if if you plan on printing two or more colors then you need to invest in a larger aparatus.
