You have several main priorities when beginning a save, and this section will run you through them.
Getting the Builders Hammer
If you've been collecting the materials that are floating by, you should have enough resources to craft a hammer which will allow you to build. Open your inventory with I (or tab) and find it under the tools section. Craft it, and you're one step closer to the floating wood shack you've always dreamed of.
Getting Food and Water
Wood and water are two factors which will determine if you survive. You can get food in two ways, growing it, and fishing. I will discuss both.