I haven't used the chauffeur drive at CDG per se but I've used it at several other places and the way it works is fairly similar.

After you cross immigration and collect your bags and begin to head towards the exit, you'll notice a signboard with the words "Emirates Chauffeur Drive". There will be a uniformed EK staff there who will guide you to your car/ ask you to wait while he will call the driver for your car. They have your contact details and I've found that if you get delayed, they will try calling you on your cell.

I assume you have booked a chauffeur drive either through the website or by calling EK - unless you book the chauffeur drive in advance, it won't be offered to you.