One of the foundations of audio editing is the mixing phase. This is where you take several edited individual tracks and mix them together to form a complete audio piece.
To begin mixing, import two or more audio tracks into your project. You can use the time shift tool to move the tracks left or right to adjust the timing.
Generally, you would stack the audio tracks by level of importance or prominence. This means narration or interviews would be on top; music or ambient sounds would be underneath; and finally sound effects or room tone would be at the very bottom. You can adjust the order by clicking on the drop down menu at the top of each track.
Once you have imported multiple tracks of audio, it is important to name each track to help identify what is on them.
Click on the drop-down menu just to the right of the close "X" button, and select name. Identifying tracks is also important for times you want to come back to an old project.
You can use the envelope tool to create fades and adjust the volume of each track in relation to the others.
It is good practice to bring in music and ambient sounds gradually. The goal of mixing is to keep sound effects inconspicuous so as to not distract the listener from the primary narrative. Rather, ambient sounds should support the narrative by adding dimension to the piece, not overpowering it.
If you need to listen to only one track temporarily without the the distraction of the others, you can use the mute and solo buttons which will temporarily shut off other tracks.
Mute will turn off the current track, and solo will turn off all other track except the one that is soloed. These are especially useful when mixing large projects with lots of tracks. (Remember to turn all of your tracks back on before the final export. It is easy to forget about a track that was muted)