The domain name will be www.abc.com. You will create your website using the Kentico Installation Manager as normal. Then in IIS you create a virtual directory under your current website and call it "support" and point it to the location on your disk with the Kentico installation resides.
After you are complete, you should be able to access your Kentico instance by going to www.abc.com/support/admin
If you receive errors, there could be items in your web.config you have to remove and add back (if needed) based on the configuration of your current site.