Do you mean above the menu in the navigation panel on the left of the template? I would also be interested in the answer to that.

Brigitte: Apologies for the very late reply. We somehow missed this post!

Your best option would be to create a new module position to accomodate your logo. For details on creating a new module position may I suggest the following article.. http://www.joomla51.com/tutorials/item/creating-a-new-module-position-in-the-header-area-of-your-template

Note: Rather than editing your templates header.php, your new module code will be added to your templates index.php (../templates/j51_florence/index.php), directly after the following...

<div class="sidebar_wrapper" style="background-position: bottom 0">

Ciarán