I've been following this article from Salesforce on how to setup a custom domain for serving up a Salesforce community. On step 2 it says I have to setup a certificate for use with the domain.

We already have a certificate for our domain, but the the instructions in the article make it appear like I cannot use my existing one and I have to create a new one instead.

If I wanted to use my existing CA issued certificate, how do I go about doing that?

I've been following this article from Salesforce on how to setup a custom domain for serving up a Salesforce community. On step 2 it says I have to setup a certificate for use with the domain.

My goal is to have a community like:

https://support.mydomain.com

We already have a wildcard certificate for our domain, but the the instructions in the article make it appear like I cannot use my existing one and I have to create a new one instead.

Do I have to buy a new certificate just for Salesforce or is there some way of using my existing wildcard certificate?