At my Home Depot, it's kept outside in the garden area next to the building.
3 cups of what kind of
nutrients? Are you puting seedlings in the system or mature plants?
You will just have to read the instructions as it varies so widely from brand to brand. If you are putting seedlings or very young plants in, you will want to delute it even further like only use 1/4 strength and slowly increase the ratio. Otherwise you will just be burning the plants and wasting nutes. IMHO, they plants only need full strength when they are flowering or fruiting. Lettuce and like plants never get over 50% solution of nutes cuz they don't need it.
You want to make sure you are putting like
nutrient requirement plant together. You would not put tomatoes and lettuce together except maybe to start out. Maters need way more nutes and they also need extra micro's and cal/mag.
Also if you are using a 2 or 3 part nutrient always add the micro first!
I turn off my pumps when I do anything to the nutes, mix well then turn the pumps back on.
Let me know if ya have anymore questions. I'm on facebook too which I check more frequently, Tri City Hydroponic Gardeners!