I've just uploaded a photo to facebook from my macbook pro and the photo is much larger than I would like it

I've gone in to 'photos' and 'edit', but there is no option to re-size the photo... I can enhance it, crop it, adjust red eye...etc... but there is no option to make the photo smaller

Can someone please tell me how I can do this.... wife is complaining the photo is too big and I need to resizeit a.s.a.p.!