PDF (adobe.com)

Add a track while adding a clip

 Drag a clip from the Project panel or Source Monitor into the blank space above the topmost video track (for a video or linked clip) or below the lowest audio track (for an audio or linked clip). Adobe Premiere Pro adds an audio track, a video track, or both, depending on the content of the source clip.
Note: If the sequence doesn’t have an unlocked track of the correct media type (for example, a stereo audio track for a stereo source clip), a new track is created to accommodate the clip.