The fob comes with an actual key...if the fob won't work, use that. If its battery is dead, there's a location on the steering column you need to hold it while pressing the start button to get the car to work. Yes, it's all in the manual, and you can read it in the car if you don't like paper along with replacing the battery (which might be covered during the warranty period).
I've had to use the key once when I was parked quite near some TV transmitting towers...the RF interference was just too high for the car to find the remote in all of the clutter.
2011 535i x-drive GT, 2014 i3 BEV