on the IOS or android? IOS you have to add tank (+ top left), fill out info. open newly added tank, press (+) top right, just left of the edit. select measurement you would like to input, enter quantity, measurement description (PPM), description if you would like, photo if you would like, check date, click save.
it took me a minute to figure out, once I did I was hooked. I really like the graph.
