You'd want to take a pre workout serving with your explode, as well as a post workout serving, you can also take it first thing in the morning if you want to, though the most important time would be during and post workout.
As far as serving size goes its up to you, just stay above a teaspoon, I usually load post workout so i'd have a bigger serving, but
ON whey has good BCAA's in it already if your money conscious.
If your taking explode then wrath wouldnt be that important since your already getting arginine and you wont need
beta alanine post workout, just stick to the BCAA's.
hope that helped.