Hi Andrea
As far as changing the overall template, there should be a place for you to "Edit the HTML" of the template. Inside the code there is probably a table width that is set at 100% or some value. Try decreasing that value to see if that
It's been a while since I used Website Tonight so it may have changed a bit but from what I remember you have to edit the overall template and there is a way to do that.
Worst case, email
support@secureserver.net and they can better assist you.
As far as adding another nav, I believe you just click on the area where you want the nav to go and edit that way. Now if there is not currently a spot/placeholder for a nav button then you have to again go into the HTML and edit the code.