Back To The Future The Game - How to take keys

1.) Go right to the toolbox getting a tire iron, and on the top of the van the radio antenna.

2.) On the left side of the van, use the tire iron and remove the spare, getting a  hubcap in the process, from your way to reach the driver's window. You must walk on the vans left side, the window of the right side is closed.

3.) Try to use the antenna to get the keys, only to realize they are too far away / Trying to use the antenna to grab the keys is impossible at the moment since Kid Tannen is extremely attentive.

4.) Tell Doc you need a  distraction and he'll gladly provide one for you.  

5.) Use the antenna to, finally, get the keys from inside the driver's booth, and use them to open the locked doors. 

6.) Tennen will start shooting at you. Time for a frisbee lesson: throw the hubcap at him, making him drop the gun.  

7.) Get the gun and shoot the chains holding Doc and tell him to hit the throttle.