The objective is for players to "capture" and hold the base for thier faction. To do this, players must turn four different Control Terminals: Alpha, Beta, Delta, and Gamma. The Alpha, Beta, and Gamma Control Terminals are located outside, and the Delta Control Terminal is located in the central building at the bottom level. To turn these terminals, players just have to "click" on the terminal and wait by it for about 15 seconds. During this time, if the player moves or is attacked, the turning of the terminal fails and the player must retry to turn it.
Once the base it turned, a factional NPC will be available at the bottom of the main bunker (in the same room as the Delta Control Terminal) to award PCs of that faction stims. These stims cost nothing, but you can only have 1 of each at a time. If you use all the stim up, however, you can get more for free.
At first, only 3 stims will be available.
If the base is held for 4 more hours, more stims will arrive. You can check with the same NPC that you get the stims from to see how much longer you need to hold the base for the rest of the stims to arrive.