After you upload an image (or draw one with the drawing tool) you can edit it with the Resize & crop tool.  

First, open the Editor by hovering over the frame and select Editor. 
​
​

In the Editor, choose Resize & crop.

This will bring up a window, which will give you the option to crop or rotate your frame.

​

Perfect for reframing an image or zooming in on some detail 👌