In reply to roelq:
Climbing with a weight vest or weight belt works well for breaking through a plateau that you may have hit with your climbing, but I'd only recommend it if you already have a good amount of training under your belt.
For you (at 58kg) I would say 5kg as an absolute maximum (you'll probably find 2,3 or 4kg enough!) the key is to pick a weight which doesn't stop you using small holds, or doing big powerful moves (these will feel really hard/weird during the first session!).
Take it steady as, as with any form of good, stressful training, the risk of injury will be higher.
You want a vest or belt that's as small, soft, and as comfortable as possible, I picked up a really nice neoprene 7lb weight belt from a martial arts store which is perfect! for about twenty quid.
Good luck!