Place new worm on the shaft of the coreless motor and check for correct alignment. Run the motor to test. If it is all running great, use metal glue like Loctite or Granville (ideally the blue lock thread version) to glue the worm in position.

(Earlier versions of the kit came without the worm, but with an adapter to fit a worm.)

Check fitting

Check how far the worm has to go on the motor axle, glue it if necessary on the axle.  It might already fit well in place with pressure fit. Use Loctite and not Superglue, as with Superglue you will not have time enough to adjust the height.

Glue motor

Glue the motor in place. I used the gel version of superglue. Just sparsely some gel around the edge of the motor opening on the frame will do the job.  Check if the worm touches the gear, but not so that it locks the gear. You need to be able to wiggle the rear wheels a bit. If you get a crunchy noise when running the model, the worm is too close.

Assemble model

When everything works well, put the parts back together.