You have to be very active in Altcoin announcement section where you will get all details about the newcoins launching and as soon as they start the thread immediately you can post about you can do translation work on which you are good and when they give your confirmation with all details you can start it.
So like this only translation work goes on. Apart from that in Service section you can start your thread about what type of translation language you are doing and which extend you can do it.
In addition to what Jayshree85 has said, once you start and you are known to be an excellent translator, they may even request for your translation services in the future. this doesn't necessarily only apply to new coins that are launching. some of the popular coins right now are still in need of translations. Because of Wiki or some news that needs them.