How can I change the link for the site on the top of the homepage?

riorick17, welcome on the XOOPS forum!

I'm not sure which link you mean, or why you want to change it and from what to what?

I need a way to get back to the main homepage of my site. And wouldn't you know it, right after posting this I found what I was looking for in the file /themes/default/theme.html in the header section in the line
<tr id="header">
<td id="headerlogo"><a href="<{xoAppUrl /}>" title="<{$xoops_sitename}>"><img src="<{xoImgUrl xoops-logo.png}>" alt="<{$xoops_sitename}>" /></a></td>

...so I changed "<{xoAppUrl /}>" to "mysiteurl"

Unfortunately the theme I'm working on doesn't have a logo image, it just uses a text link... so now I have to figure out how to add that.