I added it to the Internet tab on my Fuze, just under the homepage button and above my favorites. (Where it is on all the European versions of the Touch Pro!)
The process isn't too difficult but you'll need a good file explorer like Total Commander and if you're not comfortable editing Read-Only TF3D files, then DON'T TRY THIS!!
You'll need to edit the InternetPortal-en-US.xml file located in the \Application Data\Manila\ folder, so it's probably a good idea to make a backup of the file before you start messing with it.
Find the <OperatorLinks> section in the file.
Between <OperatorLinks> and </OperatorLinks> add this text:
Save the file and make it Read-Only again and you should have a YouTube icon on your Internet tab.