wild card ssl cert installation on SSG140

Hi;

I have a SSG 140 appliance, and I install a wild card ssl cert (.cer) file to my SSG 140.  

1. How can I make it as default ssl cert, whenever I enter https://myfirewall.company.com domain, and..

2. using this cert as my SSL VPN cert.

I can see my certificate load to appliance but when I enterhttps://myfirewall.company.com, I found that it is using self sign cert only.

Also, I have a site to site vpn, if I make my wild card ssl cert active, would it break my Site to site link>

Please help to solve this issue?