Hi dodgy, glad you've got your car!
Believe it or not any competent dealer should set this up for you before you take delivery of your shiny new car. My dealers did not set up the BMW assist etc! Pillocks. Anyhow, you need to download the form from BMW's website and they will process your 'application' normally within 3 working days. They'll give you a ring and the info. to activate the system will come through via 'My info.' on the i drive. So basically, you're going to have to wait a few days I'm afraid, unless you ring them and see if they can expedite it. The link is below.