Using the image editor

Click the image tab (1). Move your mouse over any image (don't click, just hover) and you will see some icons. The paintbrush icon (2) will open the image editor.

Select an image edit mode (1). Click the Save button (2) when you are finished.

Everytime you save an image, a new version is created and this will appear in the top of the images tab (1). Drag and drop this onto your page to use it.