Remember the last portion of your very first mission ("Insertion Point Alpha") where you had to protect Lian? Well, this is a version of that same mission. Lian isn't there and the enemies are shooting at you, plus they're coming from a greater range of areas.
This mission is pretty self-explanatory. There are two barrels you can use for environmental kills; one is partially hidden on the ground near a wall and the other is up on a ledge in front of you (think back to where you shot the very first enemy attacking Lian in the first mission of the game).
The final boss of this mission is just like Anton Girdeaux/ Red Jack: he's wearing heavy armor and carries a flame-thrower type weapon. You have to shoot the tank on his back to kill him. You can place an exploding dart on the ground to knock him over and buy yourself some time. The fact that you have an elevated position should make it significantly easier than the fight with the two aforementioned enemies.