how to attach a chassis another chassis

How to Attach A Chassis another Chassis

Example: Will attach
A. boot.ok in boot.z3d file, with
B. spoilet.ok in spoiler.z3d file
First, open the first file "boot.z3d. [such as the following figure];

then, after opening the file "boot.z3d", you click on the toolbar "File > Marge", and select the file "spoiler.z3d. [note the following images];

after that, you select "Modify > attach". then point the cursor to the frame of the car "spoiler.ok" then click again after that point the cursor to the frame of the car "boot.ok". then that its separate origin [two car frame] sekatrang into a single frame of the car.
image results from the tutorial project