Preparing For Transformation
Begin with the action figure fully transformed into Bumblebee. Face the figure toward you and bring his arms down to his sides and push his legs together. The figure should end up with all parts parallel to one another. At this point push the legs up toward Bumblebee's chest. The legs will slide upward so do not bend them.
Creating the Hood
With Bumblebee's legs secured, use your finger to lift under his chest plate, bringing what will be the hood of the car upward while the windows of the car will shift 90 degrees downward. Now bring the arms of the action figure straight up.
Final Transformation
The final step to transforming Bumblebee back into a car is to take the arms that are pointing up and bring them forward while also moving them toward the center of the figure. Notice the shoulders of Bumblebee have a rotating joint. This is what is used to guide the arms into place. Do not force them or the arms will break off, instead keep them moving until they firm into place, leaving no parts of the figure moving freely. Flip Bumblebee over and he will be in his car form.