Click on the guitar icon on your computer to open up the GarageBand program. A small window should pop up, asking you to select a new project or open a recent one. Select "new project." Another window will then pop up asking you to name the project, as well as what time signature it's in and what tempo you'd like it to be at. First, name your new project. You can either customize the tempo and time signature now or fix them inside the session window later. Once you click OK on the new project/customize window, a session window will pop up for you to work in.
Click on the "eyeball" icon at the bottom of the session window in the lower right corner. This will bring up your loop and sample library. Click on any category you want inside the loop library, meaning guitars, pianos, bass, strings, beats, percussion, effects, etc. The loops in that category will then show up. Double click on the loops within the category and take a listen and pick the ones you want to use. When you've found the ones that you want to use for your track, click and drag them into your session window. Repeat this process using various loops to make a track. You can customize the entrances and exits of each loop and sample by dragging the samples around the time line and syncing them up however you'd like. At the bottom of the session window, the metronome and time signature controls are there. Feel free to drag them up and down, making your song as fast or slow as you'd like.
If you'd like to share your song on a website or with someone, go up to the menu section at the top of the screen and click on "Share." The pulldown will give you different options. Select "send song to iTunes" and from there iTunes and GarageBand will do the mix-down work.
In the file menu of GarageBand, click on "File." The pulldown menu will give you various options. Click on "New" to begin a new session, separate from the loop and sample track you just made. Name your track as you did in the aforementioned session. A new session window will then appear.
Go to the file menu of Garageband and click on 'Track'. The pulldown menu will give you various options. Click on 'New Basic Track'. A 'new basic track' will then appear in your session window. On that track, there will be a recording button that turns red. Click on that to enable recording.
Now connect whatever interface you are using to record. M-Audio is recommended because of its ease of use and affordability. Once your recording interface is hooked up, click on "GarageBand" at the top of the menu screen. In the pulldown menu click on "Preferences." Another small window will pop up, then click on "Audio/Midi" at the top of the screen. There will be two sections for Audio Output and Audio Input. Your external recording device will show up in the scroll bars; click on it and customize it so your audio input is your recording device and your audio output is either the computer speakers or whatever external speakers you have connected to the computer.
Once the customizing in Preferences is finished, go back to your session window. When you are ready to record, make sure the small red recording button is enabled on the actual track. Also, at the bottom of the screen is a bigger red recording button. When you are ready to start, push this button and play or sing into your recording device. When you're finished, click off the recording button or just hit the space bar.