Nobody can give you that info without knowing what your account number is and which Bravenet server your guest book is hosted on.
The url is included in the copy/paste code. On the other hand you could just go to your guest book and copy the url from the address bar of your browser.
Any easy way to find it is when you are in the manage service of the guestbook click on the >view service. The direct url will be displayed in your browser box.
