Click the "Finder," open the "Applications" folder and double-click "GarageBand."
Click "New Music Project" and save it as "Sound Recording 1."
Click "Track," select "New Track," choose "Real Instrument" and click "Create."
Plug one end of the XLR cable into your microphone.
Plug the other end of the XLR cable into the 1/8-inch stereo mini plug adapter.
Plug the 1/8-inch stereo mini plug adapter into the "Line In" input on your Mac computer.
Click the "Apple" in the top-left corner of your computer screen and choose "System Preferences."
Click the "Sound" icon.
Select the "Input" tab within the "Sound" menu and choose "Line" from the drop-down menu.
Adjust the sensitivity of your microphone by sliding the sensitivity fader left or right. Sliding the fader left will reduce the volume of the microphone and sliding the fader right will increase the volume of the microphone.
Return to the GarageBand window and arm the track you created for recording. Do so by clicking the round circle next to the track name. After clicking the circle, it will turn red.
Press the master recording button, which looks like a bigger version of the button you just armed, located at the bottom of your screen. After doing so, GarageBand will begin recording.
Press the space-bar to stop recording in GarageBand.
Save your GarageBand project when finished recording.