Yes, This does need to be improved. Verbiage about uploading a square image helps.
But I think the image handling should be changed from cropping the image down to the smallest dimension to resizing the image down to the longest side. Yes, this creates the "letter box" effect. But at least heads would not roll!
Asking members to do much 'image editor' work is quite often more than they are able to do.
I recommend the free online editor http://fotoflexer.com/. It's dead easy.
thanks Clark - I'll try it out!