Select some text and press the link button in the toolbar.
To your own pages
The picker lists your own pages by name. Pick one. You do not need to remember the address. Type to filter the list once you have more than a few pages.
To anywhere else
Paste the address. A link can open in a new tab.
Email links
A link to an email address opens the reader's mail app. Your front page starts with one: "Or write to me at" your address.