Drop the spare wheel down under the car.....
Item 3 passes through 9 and 17 and screws into the top of the threaded part on the carrier frame.
Usually stuck with rust.....flood it with WD40 and use heat. Its a 6 or 7mm open ended spanner to undo it.
Good idea to put some copper grease on it when assembling
Once that is off there are a couple of fixings on the toolkit tray.