I just got NS v2.0 and i cant add marines OR aliens in my games... i dont like to play online so iwas wondering how would i get marines and aliens in my games???

The most recent version is NS 3.0, downloadable from the main site, as well as patch 4 beta A, so you would need to install:

3.0
3.0 Beta 4
3.0 Beta 4 A

As for bots, I'm not even sure those work in Beta 4 A, but you could try checking out this thread and following the instructions placed there.

http://www.catb.org/~esr/faqs/smart-questions.html

You cannot add NS to "My Games" under steam. It shows up under "Third party games" for the time being.

"Marine" and "Alien" Ns is the same game

There is no single player NS, but RCBOT and WhichBots are the 2 bots for NS.

STW.

yea i use rcbot, works well, although it sometimes crashes when u add a ton of bots.

search at Google for rcbot and u should find it

why dont you like multiplayeR? if you dont mind me asking