First, create a new project inside C2 and select any the touch demonstration to start with, there you'll learn about touch and its behaviors, including multi touching.
To make the desired behavior, simple test the origin of the touch and its ID, if the first touch (ID 0) is happening and it move from its origin, e.g. to above, the tank should move to above and so on.
Shake screen is an action of the "Scroll to" behavior, and it only works when far from the layout edges, else, it'll stuck and don't work properly. You can make a custom shake screen system, just search for it on the forum.
Before trying to add multiplayer you should read the tutorials and look inside the sample files of C2. One specific tutorial from one of the C2 creators is a good start, just hit the Tutorials button above this topic and search for it.