No online instructions AFAIK.. but it's easy (ish)..

Place bezel upside down.
Fit the polygonal (or whatever the term is) retaining spring into the lower groove.

Now fit the thicker 'click spring wire' - i.e. the thicker wire with the short 90 degree angle..
Bend it the wire into the upper 'geared' section of the bezel. with the 90 degree short bit sticking upwards.
It will be held in with tension.

Carefully pick up the bezel, turn it over and place the short 'sticking out bit' into the hole in the case at the 12 o'clock position. (Do this carefully - the retaining spring wire may pop out - if it does, refit)

Then, in one firm swift movement press down the bezel, making sure it stays flay and twist anticlockwise.
It may make several attempts, as the retaining spring will pop out.

Be firm, confident and try again & again.
Some require more pressure/effort than others.

Stewart
- Heuerville