To make sure Yousician is able to hear what you are playing, you might need to change the input level on your computer. You can do that following 1 of 2 methods:
A) System Preferences
1. Open System Preferences and choose "Sound".
2. Select your sound input device and use the slider to change the volume.
B) Audio MIDI Setup
1. Open Audio MIDI Setup and select the corresponding input device.
2. Change the input volume using the slider.
Both "Sound" (System Preferences) and "Audio Midi Setup" can also be accessed by doing a search (cmd + space) and writing either "Sound" or "Audio Midi Setup".