Definitely a good first attempt. Like Lov3 said its essential to work in layers as a safety precaution.
I would recommend becoming familiar with three things.
1. the brush window, which will allow you to set the brush roundness and angle
2. opacity and flow on the top toolbar, they will effect how quickly the brush paints
3. brush hardness and size, click on the brush icon at the top when the brush tool is selected to change these.