Lots of different ways of doing this, one is link above, another is:-
Dissolve 1/4 teaspoon of EM in 4ml of PG.
Directions
Heat the 4ml PG in the microwave @ 5 second intervals, may take up to 3 times. Then add your EM powder to the warm PG (Do not heat the EM with the PG in microwave) , Diluted mixture can then be added to your eliquid mixtures. Start with 1 or 2 drops per 5ml of liquid. add more to suit your taste.
Edit - I have no idea where I got the instructions from but have been using this method for over a year.