Picture of How to make a 360 degrees turning motor
A basic very basic arm you can make from some things laying about.

1. motor
2. Screwable pieces of toys or plastic.
3. batteries and battery compartment
4. wires

Step 1:

Picture of
First make the type of arm you want. From the screwable pieces. Hopefully it will work when you do it. The structure will move 360 degrees so make sure you make nothing too big.