Just unzip to main Notrium directory to install.
When you load the mod you have two choices: Start from the beginning or just before pHQ (With guns, this time).
Some of the new stuff won't be encountered just by playing the game, so if you want to see everything use the map editor to shove stuff in.
Notable new things:
Ability to bring yourself back from the dead (5BQR8KU)
Death looks better than simple "You got deadified" screen now
Elite marines (Assault Rifler and Dual wielder - you'll have to map edit the dual wielder in if you want to see 'im)
Enemies now drop their guns when you kill them (you can't pick them up, they're just decoration)
Sniper rifle no longer has an insane amount of ammo - just 20 now
You can now hold only a limited amount of grenades - and throw them around corners for some reason (I'm still calling it a feature)
Rocket launcher now explodes on border walls (can't make them... no, that couldn't... *idea*)
Reloading set up
Auto weapon switching made on inventory change
Quadbike now runs enemies over if you're going fast enough, rather than just relying on the omni wheel