Web server symbolic link?

[withanhdammit]

I think I need to do this with a symbolic link, but I'm not sure that's right, and I'm not sure exactly how to do what I want.

I installed a mail server and used squirrelmail for the webmail client. I can access this via:
mailserver.com/squirrelmail

I then decided that I want to use roundcubemail, so I installed and configured that, but I cannot get to it via:
mailserver.com/roundcubemail

When I look around, I see that squirrelmail is installed in /usr/share/squirrelmail and roundcubemail is installed in /usr/share/roundcubemail.

When I look in /var/www I don't see any links that show me how the squirrelmail is allowed, so I don't have any clue how to allow the roundcubemail.

Webserver is Apache if that makes any difference.

Thanks for any help!

h