I'm very light built in general,but what "worries" me are my wrists (5.2 inches) what exercises can I do to make them stronger both muscles and tendons ?
Wrist curls, reverse wrist curls, hammer curls and deadlifts without straps. Thick bar work as well if possible.
5.2"? I assume you mean 6.2" else that IS reason to worry. In any case, reverse curls, reverse wrist curls, levering and sledgehammer work (go carefully here) and grip training over a year or two, in addition to the loading with dumbbells and barbells that you will be using in your daily workouts should make a big difference. If you feel any strain use wrist wraps but ONLY on your heaviest pushing sets.
Here's a good article:
The wrist roller works like a charm. But as mentioned above, deadlifts will do wonders also.
Alternate hands while punchin the clown...
Deadlifts are great, and varieties of wrist curls