1. Create DBN
2. Generate time expansion
3. Compile and use
Generate a time expanded version of the net by choosing Network → Expand Time.
This will make a new window with a new net in it. You will probably want to resize this window to make it wider.
The new net is a regular Bayes net with each Position and Velocity node representing the position and velocity at a new point in time, with nodes to the right corresponding to later times.