1) All first thing in the morning.
2) Split dose in the morning and pre-workout.
3) Only pre-workout.
4) Pre-workout and post workout.
5) Any of the above plus before bed.
It is a very versatile supplement and I suggest you try several different dosing schemes and amounts to find what is optimal for you and depending on what your goals are at this time. I personally use some in the morning after I wake up and some before bed (I also do not use it solely to increase pumps, but taking it in the morning still provides me some pretty incredible pumps even when I workout later in the day).