To set loop points:

• set the from and thru to the time range over which you wish to loop.
• press Alt+Shift+right square bracket; this toggles loop mode on.
• now press Alt+Shift+right square bracket twice; this sets the loop range to the from/thru selection.
• If you wish to read (verify) your loop points, press control+shift+right square bracket once for “loop from” and twice for “loop through”.

note: For this to work , make sure the Loop toolbar is enabled.