Create a new GarageBand project. Click the GarageBand icon to open the software, and select the "Create New Music Project" option.
Enter a name for your song, and then select the desired key and tempo. If you cannot decide on a key or tempo, just leave the default settings and you can always change them later by adjusting the settings in your main window.
Click the "Create" button.
Create new tracks. By default, you will see one software track in your GarageBand window, but you can create more tracks by clicking the "+" button next to the eye symbol, on the left side of the window near the bottom. Tracks are situated on top of one another and span horizontally across the time line. You can use them for recording different parts of a music project. For example, you might record guitars on one track, and then record vocals on the track beneath it, followed by keyboards and then drums, allowing you to create a multi-layered composition one piece at a time.
Press the "Record" button to begin recording. It looks like a red circle and appears beneath the track list. Press the "Record" button a second time to stop your recording.
Add Apple loops to your song for background and accompaniment. To find them, click the "Loop Browser" button beneath the list of tracks. It looks like an eye. Click on any sound loop on the list to hear what it sounds like, and drag it onto a blank track to add it to your music project. You can repeat the loop as many times as you would like by clicking the right edge and dragging it across the time line.
Add effects to a track by double-clicking it and then choosing effects in the "Track Info" column that appears in the right side of the window. You can add reverb, echo, effects, EQ, or sample the different presets from the list provided.
Save your finished song as an iTunes MP3 by clicking "Share" in the menu bar and selecting "Send Song to iTunes" from the drop-down menu.