Hi Yamina, thank you for registering with TWB, we鈥檙e happy to have you in our community! 
The way it works, is that you can search for tasks in your language pairs that are of interest to you, claim them and translate them using our Kat贸 TM. You can find more useful videos and FAQs here.
Please note that we are a non-profit and we don鈥檛 pay our translators. However, we highly value their contribution and offer a recognition program.
Does it answer your question? Is there anything else you鈥檇 like to know?