Hello,
First, please have a look on another thread with the same question.
https://colorlibsupport.com/t/how-to-create-menus/
You should go to Dashbboard > Appearances > Menus and add custom links.
If you need anchors, just use them at the end of the URL, otherwise use the URL for the static page
e.g: Under construction - Awesome site in the making!
It is preferable to erase the HTTP at the beginning or the www and let the broswer redirect accordingly.
Let me know if this got it fixed or there is some other issue.
Regards