Mesh90, like agumon said, you need to have a certain tool to proceed (if you haven't completed the swamp dungeon yet, you're not in the right place). If you do have the tool, look around the map near the sign and see if there's anything that resembles a "green pad." Here's another hint: it's located in the water.
Agumon, thanks for your feedback. I understand monsters are a little annoying but I remember limiting them on maps with larger puzzles. If you fight enough battles, you should find them a lot easier to defeat. The swamp really wasn't my strongest dungeon, so I inserted a little more fighting, but it should get better as the game progresses.
If you need a hint, keep talking to the frog until it leaves the second map. You need to jump a few times, which you can only do when there's one tile of swamp between land. (If you're wondering how this was evented, I used the "Jump" command on Player Touch.) Once the frog goes to the third map, you can follow it up and walk to the very end of the path. That should trigger a scene and you'll be able to proceed.