Open the background tab. Menu → Import and Export → Import Background Image (Ctrl-B or Command-B)
Click on “Add” under Images in the tool box.
Select an image.
Select the first tool in the tool box.
Create a rectangle around the letter you want to import.
Click on the rectangle.
Click on Select Glyph under Parts in order to send the background image to a glyph. Click on Unicode if you get the message “No glyphs in this view”.