Use the crane to create a bridge to the emergency release | Mission 3: Sulaco Falls A: CM Guide

Keep in mind that immediately after receiving the task new enemies will spawn on both levels of the hangar bay. Focus on the ones on the upper gallery and in the control room. Use covers, especially since one of the enemies should be heavily armored (traditionally, use grenades or the grenade launcher against him). Don't lean out of the cover until you've secured the whole upper level.

Head for the control room; you can enter it now. Look around for any interactive objects, but don't forget to interact with the control terminal for the containers (the above screenshot).