This is the way I do it, if there's an easier way I'm not sure of it...
1. Upload pictures onto photobucket (This will resize it to an acceptable size)
2. I then take the pictures from there and save them back to my computer, I have a mac so I just click and drag it to my desktop, but you can also right click it and save image to a location of your choice.
3. Then I upload the appropriately re-sized image directly from my computer into the photos section.
Hope it helps, works for me!