Help with Invasion mode

[ForeskinJohn]

This may be a dumb question, but I was wondering if anyone could help me get started with invasion mode, I used to play quite a bit of it when skulltag was more popular but id like to start playing in zandronum. Thing is, im not sure at all how to play with zandro, or skulltag anymore for that matter, id like to know where I can get maps for the gamemode, and just how to initiate a single player game and get started fighting waves, any help is much appreciated!