Home Science Tools' website here for brief instructions.
And these are her inoculated dishes waiting incubation. I took one biology course during the course of my 19 years of schooling. Chemistry with all the redox reactions, organic hexanes, and physical entropy properties were more my thing; but, growing things like bacteria, viruses, and fungi, were not so much. Preparing these is petri dishes was an entirely new to me...so if you really want to know the correct way to do any of this...please refer to a reliable source.