Ya just export it into a .jpeg file.
Step 1.
Open up your image and edit it to your liking…
Step 2.
File –> Save as –>
In the name dialog type “IMAGENAME.JPEG”
Step 3.
Press OK/Save
It will tell you something about layers just press “Export”
Step 4.
Move the “Quality” bar in the next window to “100%”
Press “Save”
Step 5.
It will save a JPEG image to whatever folder your default is. Now just give this new JPEG file to WalGreens.