How do I make the sub menu header links, link somewhere else?

Please forgive me if this topic is covered somewhere, I have searched and searched, and either I don’t have the right terminology or I am lacking caffeine this morning. ??

I am using the WP Random Image theme by Alex Cohen https://www.mcdevzone.com.

Under the header image, I have “Blog”, “About Me”, “Travels”, “Movies” etc. I did these pages through the Write Pages section.

Since I am trying to work around another problem I am having, this is what I want to do:

I want to have, “Travels” at the bottom of the header image to actually go to a subdomain of my website. That’s the first thing. I would think this would be easy, but I’m not so sure now.

Next when someone clicks on the “Travels” link, and they are brought to my subdomain link, is it possible for me to continue using the header from WP? (Everything else would be different, I would just want the header image and submenu underneath it.) The rest of the page would be other stuff. ??

Yes, caffeine might be a good idea. Sorry if this is jumbled. Thank you in advance, please forgive my n00bliciousness. ??