Instructions
Clear out the Twin Ion Engine (TIE) fighters before you attack the Star Destroyer, as they will shoot at you and drain your health. Once you've destroyed them, General Kota will shout at you to "Bring down the Star Destroyer!"
Move the left stick (Xbox) or paddle (PS3) to the right and hold it there. Your character will grab the Star Destroyer with the Force.
Push the right stick or paddle up and hold for several seconds, aligning the Star Destroyer with the planet. You may need to tap the right stick up or down several times to align the ship properly.
Push down on the right and left sticks or paddles when General Kota instructs you to. You will hear the sound of steel groaning and your character will begin to pull the Star Destroyer into the planet.
Release the Star Destroyer when it sends more TIE fighters after you. After you eliminate the TIE fighters, repeat the process to bring down the Star Destroyer. It may take three or four tries and several minutes to accomplish this.