Basically :

1) fully compress the starter between your thumb and fingers. This will expose the "grabber" from inside the shaft
2) Press the grabber over the glow plug head so that the grabber envelopes the glow plug hexagonal nut completely
3) decompress the starter. There is no way you can pull out the starter from the glow plug as it is locked and secure if installed correctly.

I'll post a pic for you later