It depends what you are going to be doing.
The general process for silk screening
1. Print the image required onto transparent film. (usually a imagesetter) after prepping the file, one colour is pretty much a straight print, if more that one then trapping is involved
2. Burn the screen. This process uses a chemical called photo emulsion. A screen is covered with it. The film is then placed on the screen when and the screen is subjected to light. Where the light hits it hardens the emulsion. The screen is then washed out, where the light hasn't touched the emulsion (because of the film) the emulsion washes ou to allow the ink to pass through the screen.
3. The screen is the fixed to a platform and hinge, a shirt or object is placed under it and the ink is squeegeed onto the shirt.
If more than one colour is required then you have to make sure to register the screen so that the colours will line up properly when printed.
Screens come in different meshes. The higher the mesh count the cleaner and more detailed print you will get. The mesh count is the number of openings in a square inch. So a 300 mesh has 300 openings, very small and very fine while a 140 only has a 140 and the openings are larger so you get less detail.
"Silk screen printing" is rather an antiquated term in today's print industry, we now refer to this method of printing as "screen printing" as it no longer involves silk.
Because the Wikipedia site includes so much interesting information and graphics, I'm going to suggest you visit the following link:
We learn something every day don't we?