I've had a chance to take a few pics so hopefully these will help!
Push the mirror assembly away from the car to give better access.
GENTLY prise the bottom of the mirror away from the housing.
The photo that I have attached is a bit blurry but you should see the 'teeth.' These need to be pushed away from the car to release the mirror.
The other photos show the motor behind the mirror. Look for the four fittings this is what the mirror and back plate locate on to.
Once the new mirror and back plate are positioned on the motor the ring with the teeth are pushed back towards the car to lock it.
Looking at the pics of the backplate the ring is 'locked' when it is parallel / in line with the backing plate.
Hope this helps.
Cheers
Scott
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