In your template you will (most likely) see a class called "tplsection-top-after-block1" being used. This defines where the first item placed in the header section of the 'Site Layout' page is placed. You can change this to use: "tplsection-top-after-block1-block2" to position 2 blocks in the header (in this case "lists" are considered to be a type of "block" as well).
For example it might appear like:
<div id="Header" class="tplsection-top-after-block1 headerBgImage">
...
</div>
You can change it to:
<div id="Header" class="tplsection-top-after-block1-block2 headerBgImage">
...
</div>
Both blocks will be positioned after the div. If you want them inside, simply use:
<div id="Header" class="tplsection-top-inside-block1-block2 headerBgImage">
...
</div>
More information about how the template system and the classes you can use can be found here:
http://idn.interspire.com/articles/67/1/Interspire-Website-Publisher-5-Template-Guide/Page1.html
