How to set up domain mapping once SSL is installed

hi, I have just installed a SSL to my Multisite installation.

How do I force a subsite with custom domain http://www.customdomain.com.au to the http://www.mainsite.com.au/subsite as this is the domain I bought the subsite for.

I was previously advised that I need to force it for the cart/checkout. What would be the page names to do this. I take it that on the domain mapping page you put it in the very bottom section 'add pages URLs below to force https: do I just list them one under each other.

At the moment this box says array (what does that mean).

Thanks