help with playing guitar through garage band

Hi, I am trying to play my guitar, and have it play through garage band on my MacBook pro. I have the guitar hooked up to a focusrite i2i2 audio interface through a quarter-inch to quarter-inch cable then running to my computer through the printer cable that comes with it. This cable runs in to a usb-thunderbolt cable to my computer. The audio interface is working according to the visual assistance I received. Garage band does recognize the interface. However nothing will be recorded. I tried calling apple but they couldn't help. Does anyone have any suggestions.

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