You will need to draw any east-west walls or north-south walls that you want in your program.
The command to draw an east-west wall is like this:
World.placeEWWall(2, 4, 5);
The command to draw a north-south wall is like this:
World.placeNSWall(1, 2, 3);
The command to add beepers is like this:
World.placeBeepers(2, 5, 3);
This command would, at street 2 and avenue 5, place 3 beepers.
See the screenshot below for an example that includes these commands.