3. Tap the crop tool (scissors) and resize the box to cover the portion of the photo you want to keep and tap Crop. This will trim the photo to your liking.
By the way, all these screen caps with the exception of first full iPhone photo were taken following these steps. To me this is one of the most productive apps that I have. I recommend you play with it because this is just one of the ways you can use it but it does so much much more.