It is possible to edit existing sites on our SharePoint server (although, of course, I would urge you to be careful, if you are unsure about what you are doing to those pages). To open a site, follow this procedure:
Close any sites you have opened in your designer using File | Close Site.
File | Open Site.
Click on the site you would like to open (e.g.
Enter your username and password into the login dialog.
If we are working with multiple sites, we will also find File | Recent Sites useful, because it gives us fast access to open sites that we have been working on recently.