Record all the various instruments for the audio. Don't worry about any levels yet, just keep the instruments on different audio tracks.
Click "Window" > "Show Mix" to bring up the mixer display. Adjust the faders for each of the tracks to change their volume. Bring out important instruments in the mix while burying the background elements a bit. Isolate tracks (press the "S" button on each mixer track) to hear them alone. Isolate several tracks at once (press "S" on all the tracks you wish to hear) to hear how they relate to each other.
Add any effects or spot edits to the tracks that need it. Certain effects to consider are reverb, which adds a slight echo to a track giving it a bigger sound, or fades, which can bring the volume up or down during the course of a track. Spot edits that might be helpful are pitch shifts for missed vocal notes and rhythm shifts if a drummer ever gets off tempo.
Use the EQ (equalizer) and compressor plug-in to affect the dynamic frequencies of the tracks. An EQ plug-in will adjust the frequencies of a track to fit within a certain range, which can greatly affect their sound. A compressor brings down the highest high frequencies and lowest low frequencies to give it a more even sound.
Click "Track" > "New" to bring up the new track window. Choose "Stereo" from the drop-down window then "Master Fader" from the second dropdown window.
Click on the new Mastering Fader and choose "Maxim" from the plug-in window as well as the "EQ" window. They will both pop up on the screen.
Adjust the master audio levels from the "Maxim" plug-in window. Any moments where the meter in the window goes up into the red are clipping moments that will sound distorted on speakers.
Adjust the track's frequencies in the "EQ" window. Remember that small movements in EQ will make a big difference in the overall sound.
Listen over and over again to the track making the small mastering adjustments. The mastering process in any program is about finding the perfect overall sound to match the track that you are creating; there is no setting that works for every recording.