You shoud get 2 Backpacks - just assemble them place static weapon anywhere and use it.

As well, if you deploy them at your base or outposts, and place troops, they will make use of them.

no, I used the "steal static" interaction option. How do I retrieve the static?

As LoKi said, after "steal static" there should be 2 backpacks on the ground. If you stole it on top of a building, the backpacks might appear on the ground level, not on the level you stole it.