You can, if you used EZ-Script. I would start by building your robot first Start by adding piece by piece. Once you have built a robot, the questions like this will make sense.

I just wanted to press a button designed for left arm, and the controls work for the left arm. Then, if I press the button for the right arm, the controls work for the right arm.

Why not use the digital joypad for the left arm and the O X Square & Triangle for the right arm? It'll be a lot easier that way if you are just starting to learn how to use ARC.

Well I kind of wanted to have the the O X Square Triangle be noises/sounds to say. If I did it your way, is it possible to have the select and start button make noises?

Add joystick control to ARC and take a look at the button mapping to see what is available. Then work out what you want to put where. I haven't looked in to joystick control yet as I'm building the robot first then going to worry about controls, but based on the default joystick panel you have 13 buttons you can set (I don't have a PS3 controller so can't see what happens when that is selected).

The best thing to do is play with ARC. Add a joystick control. Setup the PS3 controller and go in config. When you press a button on the joystick the correct button is highlighted in the config so you can find out what works and what doesn't. You don't need the EZ-B to do that, just download, install and play.

Ok thanks :)

Is it possible to add more spaces for controls?

To have the analog joystick switch between servos, the new ARC version has Virtual Servos which makes it easier. Look for this project in the Examples button within ARC: Example - Script - Joystick Switch Between Servos