Make sure you downloaded the client here:
http://us.runesofmagic.com/us/downloads,client,us.html
Just extract it to your desktop then run the program. The patcher should start up, it could take several minutes up to a few hours to catch up to the current patch.
While the patcher is running, do not touch the client until the "Start Game" button is orange and clickable. If its not, then the patch is not done. Remember, it could be awhile until it finishes patching.
Hopefully this helps, not sure if I covered your questions but that's as best as I can give