You control where you go and what you're going to do next in
Eco-Creatures: Save the Forest from your Mana House in Wood Square. I highly recommend that you start by tapping the guy with the beard to start the tutorials.
When you first start the game, you'll only have a few tutorials to choose from. They will teach you the basic controls, all about trees and planting them, all about your magic and how to use it, about Mana, and about the creatures you control. The more tutorials you do and the more stages you complete in the game, the more tutorials that will be available.
When you feel you're ready to take on the first levels, just tap the up arrow on the touch screen and it will take you out off Wood Square and show you a larger map. To launch any of the tasks, just tap them. After you've beaten the scenario, they'll still appear on the map for you to play again if you would like, but the icon will be changed to a star so you know you've beaten that one. You'll only start out with a few stages available, but after you beat them, it will unlock more.
You will have to be careful with Dorian, especially at the beginning. He does not seem to have very many hit points at all, so you have to move him out of harm's way as quickly as you can. But when he dies, he is revived at the Mana Tree in the middle of the level, so you don't lose the level, you only lose the time it takes to bring him back. The only way you lose a level is when your Mana Tree is destroyed.
There are many other things you can do from your Mana House. Try tapping on everything just to see what all is there. Or you can look it up in the manual if you don't want to explore on your own. You can choose to play online, either with the local ad-hoc connection to someone near you or to play against other people on the internet, after you unlock the multiplayer option.