Here is how you can edit the URL and rename the tab for a page that is set to open a URL (rather than a regular page on the website).
To create new pages, see this help article.
You can access the pages section by clicking "Pages" on the left menu.
Access the page settings by clicking the gear icon next to each page.
Rename
Click "Rename" in the page settings to edit what name appears for that tab on your website. Once you edit the name in the popup that appears, click "Rename."
Edit External URL
Click "Edit External URL" in the page settings to edit where someone is sent when they click that tab on your website. Once you edit the URL, click "Save."
As always, when you're ready to push your changes live to your website, click the "Republish" button in the top right corner 👍