On this page of the FNAF Security Breach guide, you can find a detailed walkthrough for the Get Out mission. .
After freeing Freddy from the room, enter it - from now on you will control the animatronic. Go through the door with the robot icon. It will lead you to maintenance tunnels.
Follow the linear path until Freddy takes control and drops you off at the first aid room. Enter it and you will witness a conversation between the animatronic and the guard.
After the dialogue concludes, get back to the robot and continue along the path. At some point, Freddy's power levels will be depleted. When that happens, you need to leave him again.
In front of you you will find a charging station - use it. Go through the door to reach a corridor. Continue by proceeding through the door on the right. You'll encounter Chica - to distract her, you need to return to the corridor and rattle the cans.
You can now go thorugh the room and past the animatronic. Going further, you will reach a locker. Go through it and then save the game at the terminal.
A escape sequence awaits you. Follow the corridor and turn at the passageway marked with "lobby". When Chica joins the chase, follow the white and pink corridor. At its end there is a staircase that will lead you to the security room.
After a short while, a button will activate that will allow you to leave the room. After leaving the room, save the game and go further down the corridor.
Now a sequence awaits you in which you have to avoid Chica. The easiest way out of here is to stand around the corner and watch when the animatronic passed you by. When she does, wait for her to finish rummaging through the garbage and follow her.
If you managed to complete the sequence, you will end up at the main exit. At this point, this task will end and you will have to look for an alternative exit.