YEP is yeast liquid culture media. You'll probably add Glucose from 50% Glucose Stock to it to make YEP + 2% Glucose.
If there is none on the shelf above your bench, stocks come from the glass-fronted cabinet inside J330. If you take the last or second to last bottle write a request for more to the student helper on the dry-erase board inside J337.
If you need to make more see YEP Liquid