I have a 2008, but it's also non iDrive so likely the steps are similar for you...
First, make sure your phone is in "Discoverable" mode. (Bluetooth on, ready to be paired with something....in this case, your car.)
Then, press the MENU button. Upper right corner of the head unit.
Then, select the PHONE option.
My pic shows my phone name (since I've already paired my phone), but you want to select the BT option (BT = Bluetooth)
Then select PAIR
This then takes you to a screen where the car starts looking for phones to pair with. I unfortunately can't show your specific next options since mine is already set up (and I don't want to unpair it just for this example). But what will happen (hopefully) is that the head unit display will eventually tell you it found a phone and ask you to either enter a code on the head unit OR enter a code on your phone. Sorry....this step seems to be a bit variable for different phones and different attempts. In my case, the CAR asked for a code, and I just entered 1 2 3 4. (if my phone gave me a code, I'd enter that instead on the car) That then results in the pairing, and you should be good to go.
I've had this basic process work with Motorola as well as iPhones.
Hope this helps.
(sorry for the crummy phone pics, but this was quickly done)