Some silly b****r has put your locking mechanism on the wrong way round, you need to rotate that assembly about a third of the way round, at which point your reflector will line up properly.
See the white lines on these two heads:
While the solution is simple you have to remember flash heads can be very dangerous as they store a lot of energy (less of a concern on a baby head like this but even a small shock is unpleasant) and there's a couple of small parts in the locking mechanism. If you plan to go ahead give it a few days to fully discharge to be on the safe side and use some gloves to avoid any accidental shocks or marking the flash tube.
Unclip the small metal spring attached to the earth around the flash tube
Carefully ease out the flash tube (small ones are delicate)
Unscrew the 3 screws
Remove the reflector cover
The mount locking mechanism should also be free (there may be some more screws I can't remember on this Interfit model) but when it comes loose try to avoid letting it fall apart as it's easier to keep as one piece
Turn the mounting mechanism about a third of the way round
Then repeat the process in reverse and you're done.
If you don't feel comfortable doing it and you're near SE London you can bring it round and I can do it for you, worst part is dealing with the stupid spring thing on the flash tube as it's so fiddly.