after you beat the elight 4 go fly to Veilstone City. go down towards the man in the cave except stay to the right. There should be a new opening that wasn't there. When you get there go in it. On the upper left corner it should say spring path. Keep going in there should be a doorway. Go in and there will be grass. exploren the grass and were you can userock clime. Go up it there will be another lake. That lake is the fourth lake. Go all the way back and use rock clime again. There should be a cave. Go in. Keep going forward. It will be very annoying becaus of all the pokemon battles. But eventually you will get to Garatina.