Step 1: Get the patch cord.
Step 2: Place one end of the cord inside your phone and the other inside the port to the right of the head phones plug-in.
Step 3: Go to Apple, System Preferences, Sound, Input, and Line In.
Step 4: Go to Garage Band.
Step 5: Select Create New Podcast Episode, and name it anything.
Step 6: Hit the plus sign on the left side, and then select real instrument song.
Step 7: Click record and play your song from your phone at the same time.
Step 8: Select share, and send song to iTunes.