I just attached this picture from yesterday and it was re-sized automatically. The original size was about 2mb and it was re-sized to 95.5kb when I clicked upload. I didn't need to do anything special.
I have also used a free program called VSO Image Re-Sizer when I have needed to scale down the size of a picture. Another option is to open an account with Photobucket and upload the photo and then use the url.
Edit: I just saw the picture was from an iphone. Should have bought an Android. J/K