You have your first face, but your model is not yet a full 3D object. You are going to need to give your object some height to give your printer something to do. Before we do that, let's learn a little more about our face and how it will behave.
Extruding to make 3D objects
Understanding and viewing face normals
Although it is completely flat and 2D, your first face already has an inside and an outside, a front and a back. A quilt square is also flat, but there is a definite outside, the part with the pattern that will be seen, and a definite inside. Your face doesn't have the fancy colors of a quilt square, but you can still tell which part is the "front" and which part is the "back." The 3D...