Well, I've never really thought that there would be a need of any documentation, as the clients normally have a pretty straightforward installation procedure and pretty intuitive interface. GameRanger is probably the one I have most experience with, you just install the client, it should detect the game on your drive and you should be good to join games. I'm a bit less familiar with Voobly but I want to remember the process being about the same. I think it has the bigger community of the two as well. Both of them should just launch the game for you once someone opts to do so.
Give it a try, and come back if you run into any problems!
//The warrior of Isola
"I lack quotes that demonstrate Humor Intelligence or anything about me."
Pineapplefish
Cleidopus gloriamaris