Multiple inputs to Garageband issue

I followed all the instructions I could find on Google but can't resolve my issue.

I wish to plug in my APOGEE Mic for vocal and my Electric Guitar via Rocksmith cable simultaneous to my garageband, however, the garageband only takes or detect 1 input. For example the Mic and not the guitar. When I unplug and replug the guitar, it detects, but Mic went missing. Its one of the other.

How do I get more than one input like everyone else? What am I not doing right? Thanks