Most hosting platforms will provide you with hosting space that includes the ability to host multiple domains.

Ok so your host gave you a dedicated ip address. You buy an SSL certificate great everything installed fine and works.

Now, you probably want to add a second or third website. Well on a shared host 1 dedicated ip is all you can get. You can only install 1 certificate per dedicated ip address.

To run multiple stores in SSL with 1 dedicated ip address under multiple domains, you now need to upgrade your SSL certificate to what is called a UCC Certificate. This allows multiple domains to be listed under 1 certificate.

note: do not confuse UCC with Wildcard...these are different animals

As stated above, godaddy offers this UCC as well as many other companies. They can do as little as 5 websites and upwards of 100 or more.

So this will be an option for quite a few people and for install instructions contact the vendor that you purchased from.

Hope this helps.