LEGO STAR WARS: The Force Awakens

The walkthrough writers give a good description on completing the level:

First off, as BB-8 you should roll into the foreground and right and access the C-3P0 terminal. He won't be able to do anything and you'll get:

Now access it as C-3P0 instead to get the door open. Head in and slice the red line with Finn's lightsaber, and then rebuild the track. Push the ice block out into the main area, then smash the crate of salvage in the center-foreground of the main area. Multi-build left so that the left side of the ceiling track is complete. Hop on the BB-8 pad in the foreground and move the crane right, up and right. Switch to Finn and smash the ceiling multi-build. Rebuild right and get back on the BB-8 pad, and get the ice block with the crane. Smash and re-build the track once more to be able to pull the crane left, down and right, so that the ice block is dropped near the main locked door. Go and push the ice block right up to the BB-8 switch, and then use that to turn on the X-Wing thrusters. Rebuild the pieces that drop out of the ice block and jump on the resulting lever. One side down.

Switch to Leia and access the green panel to the left of the main locked door (match the symbols to progress). Approach the three soldiers as Leia and press to command them. Lead them to the four grapple points left of the door and pull the crates down. Jump on the lever at the top. BB-8 can now access the switch at the top of the door. Head all the way around the corridor and wait for three more Resistance members to assemble to the left. Command them again as Leia and stand on one of the four red switches on the floor in the center. Once they all stand on one, the display to the right turns on. Get on the BB-8 pad and turn the left pipe twice and the right pipe twice. Deal with the BB-8 locked directly in front of you to start a cut-scene.

As Finn, head all the way around to the left until you see a vertical wall-jumping section. Finn can jump up this chimney with his lightsaber, and then use the saber to break the battery on the back wall. Multi-build it left to bring your comrades up halfway, then smash and rebuild right to bring them the rest of the way. C-3P0 can now access the terminal to the right and you can head into the unlocked area underneath you. Smash the glowing object in the middle and rebuild the transport. Hop on it and ferry the cargo over to the slot in front of the Falcon. One down, two to go.

Head right of the Falcon and have C-3P0 talk to Nien Numb, the waving red-suited alien in the corner by the locked area. Get 3P0 and BB-8 onto the lift with Finn and head up. Run right and smash the glowing object, multi-build the debris left to turn on the left-hand screen. Get on the BB-8 pad and maneuver the gold box on the screen across the conveyor belts. Back downstairs, get Leia over to the Resistance terminal right of the blue barrier and crack the code to switch the barrier off. Command the guys inside and shoot the gold box to get everyone else shooting at it. Build the ice-cream hover thing to get Nien Numb to open the remaining door on this side. Smash the glowing object in there and again rebuild the transport. Take it over to the Falcon. Two of three.

Get Leia to command those Resistance guys to the right again and head alllll the way around to the left until you reach a massive block to push. Leia and the Resistance can push it along until it's picked up by a crane. Leia and Finn can then pull on the two grapple points, rebuild the transport, and take the final piece of cargo to the Falcon.

Here is a video walkthrough:
Credit to HappyThumbsGaming.