Here's how to use it:
Add an image using the toolbar in the text editor.
Select the image
Click the "Image editor" button shown on the center of the image.
This will bring up the Image Editor UI.
Alternatively, you can also edit your images from the media file picker. Hover over the file you’d like to edit and then select the paintbrush icon.
You can now easily make your images pop without going through the hassle of finding and using a desktop image editor. The Image Editor allows you to make a wide range of changes to your images, from adjusting the contrast to applying filters.