A step by step guide to resizing of images...
RESIZING IMAGE
The quickest and easiest way I've found is to use a site called picresize.com ---> http://www.picresize.com/. It allows a quick way to resize the image to the maximum forum allowable size (i.e. 800 pixels width) without the need for installing third party software.
Click this link PicResize Website
Click 'Browse' to locate the file on your system you wish to resize. Once located click Continue....
SELECTING IMAGE SIZE
From the dropdown list select 'Fit to Screen 800 resolution. This sets the size to the 800 pixels width, which is the maximum allowable forum image upload size.
Then click the 'I'm Done, Resize My Picture' button to resize the image.
The next screen will prompt you to decide what to do with your newly resized image. Just click 'Save To Disk' to save it to your PC.
Voilą! the image is resized and saved.
Then just follow the instructions on THIS THREAD to upload the image to the forum.