The walkthrough writers give a good description on completing the level:
The first section is an on-rails flight sim - no trouble at all, you don't even have to move much to get through it, let alone shoot. In the free-fly section, just grab four missiles and direct them at the four pink strike points.
In the next section, use Rey's staff to jump right and head through the corridor. Climb the red pipe at the end and then hop left across the handles to sneak past the troopers. Smash the stuff to the left to build a staff point and winch it around. Get FN-1824 upstairs to pull on the handle. Go up as Rey and deal with the enemies and then break the centre blocks. Multi-build right to make a grapple point for your captive Stormtrooper. Smash and rebuild up to get him to the grapple - pull it down and then send him over to the right using the grapple. He can then access the First Order terminal to make a bridge for Rey. Send her up the climbing wall to the right, destroy the box and rebuild the path, allowing you to push the plug in from left to right. Jump down and head through. Rey takes the top corridor, while FN-1824 takes the bottom. When Rey is blocked, get FN-1824 to the shining block and smash it. Multi-build right and smash, then left and smash. Rey can pull down the lever on her level. Head up and right, smash the shining blocks and rebuild. Ride the platform up and then head left as Rey. Follow the jump points left, up and back right (careful of a couple of quick-time events when Rey loses her balance). Head around the corner and pull the lever at the back. As FN-1824, you should head right and smash the boxes to create a ladder, allowing you to get up top and swing on the grapple point to meet up with Rey. Access the First Order terminal to the left, and then Rey should use her staff to climb up to the end of the section.
After the cut-scene, run towards the screen to enter a large chamber. Head left, deal with the Stormtroopers and then pull on the grapple next to the big red cylinder. Build a bomb from the pieces. Jump straight down and deal with any enemies. Have Chewie pull on the handles at the back of the bottom floor. Multi-build right, smash, multi-build left, and you'll end up with a Sentry Droid. Send that droid over to the right a bit and onto the square platform in front of the bottom half of the red cylinder. This will raise some junk that you can rebuild into a second bomb. Head back up to the top platform and right. Deal with the enemies and then shoot the two targets over the red barrier. Head up the grapple point and get Han to the scan point. Look up and left for a dark grapple point on the ceiling beam to reveal it. Swing across and smash the box to rebuild the path. Push the block off the platform. Have Chewie blow up the metal box with a thermal. Rebuild the pieces into bomb three of four and then jump down to the lower level again. Head right and set off the sentry droid. Head off any enemies and smash up the droid to stop reinforcements. Have Han smash the pipes in the right corner and pick up the wheel. Smash the shiny box in the background and multi-build. As Chewie, head left until you see another shiny box to the right of the red cylinder. Smash it and multi-build left. Pull on the handle, switch to Han and have him place the wheel he picked up and turn it, and pull on the hook once it's in place. Build the last bomb.
Here is a video walkthrough:
Credit to HappyThumbsGaming.