This Ableton Learn Live clip covers the two ways to add tracks in Ableton Live: right-clicking in the empty track area to choose a track type, and using keyboard shortcuts for speed.
The shortcuts for each track type are: Cmd+T (Mac) or Ctrl+T (Windows) for Audio, Cmd+Shift+T or Ctrl+Shift+T for MIDI, and Alt+Cmd+T or Alt+Ctrl+T for Return tracks.