Hi Joel, welcome to the forums.
If I am understanding you correctly…The G4OAC5 is a digital output module, so its either on or off. You can not set ‘the output voltage levels’ on that module.
The Pi Carrier board only supports digital input and output modules, not analog.
So, that said, to turn the module on or off, we need to know what software you are planing to use on the Pi.
There is a lot of information and code samples over on our developer site; http://developer.opto22.com/pi/
I would for sure, without question, go and have a look at each page on that topic and you will probably get all your questions answered… But, if not, just pop back here and ask away!