Here are a few tips to decrease the risks of injury.
As a beginner, prefer problems that are less than 3 or 4 meters high and with a good landing (even ground, with no rocks/roots/etc)
It can be reassuring to have several crash mats to cover a larger surface on the ground.
If you climb with a group, you can also ask your friends to move the crash mat while you're climbing, so that it always stays right below you.
To help your friends climb safely, you can offer to be the spotter.
The spotter redirects the climber's fall to land safely on the crash mat.
Careful: don't try to catch the climber yourself, you migh injure yourself!
It can sometimes be tricky to go down from a boulder once you're on top. Check the descent beforehand — especially if you're alone!