How to get a scanned photo resized for posting?

How to get a scanned photo resized for posting? [+ favourites]

I'm being a bit of a computer numpty here...
I am trying to post a scanned photo in Photos of Ourselves, but it isn't happening. Any tips?

oooh, and now its just happened somehow, I should have been more patient that's all, lol.

(still don't know how I did it though, just fiddling around and cropping the hell out of it ha ha)