Ok Justin its a pleasure
First you have to find the starter ,important is that is a good starter whitout competitor or pollutant inside ,it have to arrive to you in good condition i.e. Est during shipment not high temp.
Then you place in a acrilic or plastic bottle with an aerator adjusted on about 5-7 bubbles for second and place front a light the bottle, light 6000k is best the one for the house 20-25 w is ok
You leave it there for about 4-5 days to acclimate the phyto
Then you start to duplicate it with water ,same water used for the water change of the tank but prepared in very clean condition you have not to contaminate the colture with bacterias or competitor also the ones coming from your tank
At last you add 2.5 ml /1lt of phertylizer to the water you have prepared
And start to duplicate the phyto i.e. If you have 250 ml of starter you add 250 ml of new water after a week again you add 500 ml of new water after other week
But you in any case do not add more new water of the one you have in the colture
Very important phertylizer must be very good ask to the one who give you the starter where he take it and take the same