There are two storys the first one is storege and the second is whatever. (you add your own details at the end).
Step 1: Step 1
Get a 12 by 4, a 10 by 4,and a 6 by 4 flat lego piece.
Step 2: Step 2
Connect the three pieces by any fat 4 by 1.
Step 3: Step 3
Put two fat 2 by 4 lego wheel connecters in the back of the truck and one 2 by 4 wheel connecter in the front. Then fill in all the gaps. (you could take away one of the back connectors like I did).
Step 4: Step 4
Count four bumps up and put a door and build a wall around the border as shown below. Add wheels to all the connecters.
Step 5: Step 5
Add another wall on to of the legos below.
Step 6: Step 6
Add antother wall.
Step 7: Step 7
Add one more wall.
Step 8: Step 8
add a roof to the wall.
Step 9: Step 9
Start to built the cockpit on the front of the truck. then add a roof.
Step 10: Step 10
Build 1 level around the perimiter of the truck. Then add any details you want.