How to edit the url on a Public Web Site using O365 P1?

Hello,

I have the Office 365 P1 Plan and recently updated pages for my public web site and changed the names of a few tabs.  Can you please provide the exact steps to update the url for consistency?   I've search a number of blogs and the initial instructions differ from my Site Settings. 

Please tell me how to edit the url on my public web site using the P1 O365 Plan.

Thanks.