Changing a web page title

If you need to rename a web page you can do this by opening the page and changing it's title.
 

Changing a page's filename will change it's URL. It is not recommended to do this with a website that has already been launched. Changing URLs will result in broken links in Google Search, and bookmarks to the original URL will no longer work.

You should instead change the page's title, or create a 301 redirect if you must change the filename/URL.