Before you edit a page's alias, check if there are any redirects for the page.
Be careful when clicking Add alias or you will end up with 2 working pages with different URLs. This confuses your analytics and users.
To get to the screen where you can edit aliases:
You can click on the Manage URL aliases link on the right side of the page's edit screen.
You can also get to the aliases screen by rolling over Configuration, then on the dropdown menu roll over Search and metadata, then click on Aliases.
To edit an alias:
Type or paste the end bit of the URL into the field and click the Filter button.
Choose your page from the list below and click on the Edit button on the right.
You'll see 2 fields, the System path and the URL alias. Edit the alias field and click Save.
When you edit an alias, a redirect is automatically created.
