To de-select > Select menu > None
click once to select a region of similarly colored pixels
roughly draw the boundaries of a region
View menu > Show Grid > will display the grid on this image
Image menu > Configure Grid > set the grid size for this image
Image menu > Scale Image
select the region with any select tool
> Layer menu > Transparency > Add Alpha Channel
- this may already be done
> Edit menu > Clear
- or click Delete
You'll need to save as a PNG, or another format that supports transparent backgrounds
- JPG does not support transparent backgrounds
File menu > Export as > type in the file name with the extension you want > complete dialogs