Create a multitrack file

Choose File > New, and select any of the following:

Multitrack File: Creates an empty multitrack document.
Multitrack File From Video: Inserts the open video file as a clip on the Video track.
Multitrack File From Waveform: Inserts the open audio file as a clip on track 1.
Multitrack File From Channels: Inserts each stereo channel from the open audio file as separate, mono clips on tracks 1 and 2.
To edit stereo channels separately, select Multitrack File From Channels.

In Editor panel, Tracks menu provides alternative method for inserting open audio files into new multitrack files