Go to Styles & Templates > Style Manager. Find the skin you want to make changes in on the right side of your screen. Click the drop down menu and choose "Edit Templates". Find the FORUMHOME template and open it.
Find:
Code:
<ol id="forums" class="floatcontainer">
Replace with:
Code:
<ol id="forums" class="floatcontainer">
<div class="homebox">Some nice text here. You could add text or just add your image as below:<br /><br /><img src="http://lenmkaiser.com/images/seagull.jpg" alt="Len M. Kaiser Photography Seagull" /></div>
Click the "save" button. Now open additional.css and add at the bottom:
And click the "save" button. Your box should be there now. Of course you will need to change the text or take it out completely and change the picture you want to use in that area from mine to yours. I'm assuming you know some HTML and can handle making those changes, if not then let me know and I can help you further. I've attached a screen shot of what it looks like on my dev site. You can see it in THIS link as well.