Do you want to add the pictures as background images (where text, etc. goes on top of the images) or as regular images?
Your pictures have to be facing left or right to start with, so that needs to be done in an image editor like Photoshop, Gimp, Paint.net (
http://www.getpaint.net), an online image editor, etc.
Load your pictures into Other > Resource Manager in XSitePro.
To add a picture as a background image, go to Page Layout > Left/Right Panel > Background Image. Choose the picture from the drop-down menu. Then got to Other > Web Site Settings > Image Tiling. Choose the tiling you want.
If you don't want the image to repeat at all, you'll need to add some CSS to manage this. Go to Other > Global Scripts > HEAD section and add the following:
Code:
<style>
TD.XSP_LEFT_PANEL_SPC {background-repeat: no-repeat;}
TD.XSP_LEFT_PANEL_2 {background-image: none;} <-- you may have to add this (for the Left Panel only), depending on your situation
TD.XSP_RIGHT_PANEL_SPC {background-repeat: no-repeat;}
</style>
To add a picture as a regular image, just right click and choose Insert Image.