What is the exact procedure to update the maps, I have a disc from a friend but what is the procedure???

Ignition on / off

Do I push any buttons etc etc

 

You need to have the ignition on so that the navscreen is operational.
Go to the boot & eject the current disc, then load in the new disc.
Any software updates will start automatically.
DO NOT switch off the ignition until the updates complete. You'll see flashing 51 & 50 (or is it 52?) on the outside temp display while the nav screen is black. Whatever you do, DO NOT PANIC, and don't switch off the ignition!
The update can take up to 10 minutes or more. Once it's done the nav screen should come back on & you'll have lost all your stored addresses and previous destinations. You'll also have to re-set your home address, search by country etc.
That's what I did and it worked fine...