You must have originally applied and been approved for DACA (find instructions here).  Your initial two period must be close to expiring AND you:

 1.  Haven’t left the United States since on or after Aug. 15, 2012, without advance parole;

2.  Have continuously resided in the United States since you applied for DACA that was approved up to the present time; and

3.  Have not been convicted of a felony, a significant misdemeanor, or three or more misdemeanors, and do not otherwise pose a threat to national security or public safety.

If you have been arrested for any reason or found yourself in immigration custody, you must consult with an immigration attorney before applying.  Don’t forget this program is discretionary.  USCIS can and will deny your application if you don’t prepare it properly.