How do I use a Page Menu Tab to link to another website?

Hi,
Using Generate Press Premium with latest updates.

Please help. I would like to have my "Book Now" menu tab send people to my booking portals website as they host the actual booking calendar.

meaning you press the "book now" tab at the top of my page & it sends you to bookeo.

I cant figure out how to do this? I have the link to the bookeo page, I just don't know where to put in GP to make this happen.

I would appreciate any help please.
Thank you,

http://www.puzzlerooms.ca