How do I capture a resource node?
Solution 1:
You don't. The commander builds them, as either Alien or Marine.
As marine, all structures require power in the room to work, so the commander will also need you to build the power node in the room. To build as a marine, look at the structure and hold your build key (default e).
As Kharaa, all structures must be built on creep, so the commander will connect the room to the creep with cysts. Kharaa structures will slowly build themselves, but if you are a gorge, you can use your heal spray (default right click) to "heal" the growing building.