This instruction will show you guide how to install outside mirror glass and cover trim for Mercedes-Benz E-Class W212. The cover we used fits for W176 W246 W204 W212 W221.
Here is a similar topic article for further reference:
Remove mirror glass
Lift bottom cover
Lift catch hook and remove trim upwards
Install new double-side tape
Use torx T10
Install new cover and put the mirror back in
More cases about W212, please refer to BENZ E-CLASS W212.