Please download this free image editor called Pixia from
It is very easy to use.
Just open the image to be resized/trimmed
From the toolbar select Image-->Make Resized Duplicate
Specify the new dimensions.
The new width should be a maximum of 800 pixels.
Then click on File-->Save as
and save the file with a new name.
Upload the new file using the Image Shack toolbar or Photobucket.
Please follow this else the post will look very cluttered.