Generally speaking, this is going to take some work on your part. Firstly, you're going to need to modify your CSS file,
style.css. Here, you'll need to adjust parameters such as .container and .containerbg widths to accommodate the width of your new 3rd column (assuming you're not wanting to loose any existing space). Since the background image of the page is designed for the current container width, you'll also need to modify this image to match your new container width.
To create the new column itself, you'll need to add some new CSS code to your style.css file. This may include the style for the <div> tag that will make up your 'column'. You can model this after the existing sidebar code,
.home #sidebar. And instead of align:right, you could use align:left to place the new column on the left side of the screen.
Obviously this will entail some work. It's a lot to simply ask anyone here to do for you, but it will provide you with a good learning experience. Of course, if you're willing to pay for the help, you can place a job ad in the "Jobs" section of this OSClass forum.
Good luck!
