Call for Artists, Making Money at Juried Art Fairs, Craft Shows and Festivals
From what I can tell, facebook cover photos are 851px wide by 315px high, which seems like a really odd size to me. You could try cropping it to that size. If the photo you want to use doesn't work well with that aspect ratio you could make a collage of photos that fit in that size or you can add borders to make it that size. I'm sure there's other ways to work around it.
The 851 x 315px is the size you need. What you can do is take 2 or 3 photos and merge them together in a photo editing program.
With Photoshop you could make the first photo the correct height (315), then make the canvas 851 wide. You would then use the place command to add other photos. Other programs have similar options.
Thanks Lisa & Dave. I didn't know those sizes. Guess I just got lucky the first couple of times I put cover photos on my FB pages. They went in magically and look good. Trying to convert this nearly square image isn't going to do it I see. But I understand what you are saying. I don't have photoshop and don't want to add other photos. So guess I have to start over.