Terrific!
So all you need to do is open the photo in Photoshop, choose your crop tool, and enter the values they've given you:
When you crop it, it will enlarge a LOT on your screen. That's a good thing.
Then when saving the jpeg, choose 7 on the 0-12 quality scale. That will give ample quality, but keep the file manageably small. (Oh, and make sure you choose "Baseline Standard" in that window also).