Changing a page title can be done using Properties.
Select "Standard" and enter the new title.
Only change the page name (URL) if is absolutely necessary. There may be pages that link to your page (referring pages). Pages linked inside CommonSpot will be updated, but bookmarks made by users will break.
Under "Actions" choose "Rename Page..."
Type in the new name (this will be your new URL - keep it short) and use the orange circle to copy it downward.
If you have a page for which the title on the page needs to be different than the title that shows in the Navigation, you can do this using a redirect.
Create a New Page with the title that you wish to have in the Navigation. Use a very short URL (no one will use the URL) and the title you want to be in the navigation.
In the Standard Properties screen where you are entering the Name, Title, and Description, before you click next set a Page Expiration. Choose today's date/time. Select Redirect to a Page/URL. Use Choose to find the original page.
Add the new page to the navigation and remove the original page from the navigation.
Also add a text block on the new page that reads: "This page redirects to _____." That will remind you if you try to author the page. When you do open the page in authoring you will get a warning which you can just ignore (click OK).
When someone clicks the link in the navigation to the new page, they will be redirected automatically and instantly to the old page.