how to remove the face on a Titan wrist watch?

You can't remove the glass face.
To access the hands take the mechanism from the case.

Remove the back of the watch.
Then remove the winding shaft stem - one screw
Then take the watch mechanism out of the case.

Or - as suggested below - have it done by an expert.

Good Luck...
March 2017

Why not ask a jeweller/watchmaker to look at it?

acp
March 2017