Place it into a glass with alcohol, it must free flow without touching the bottom or walls of the glass. Following is a copy from Wikipedia Very easy to use.
Glass Alcohol Meter 0-96% Areometer for Home Brewing Wine Making with Hard Case
Hydrometer alcohol meter
1 Set Hydrometer Home Brew Wine Alcohol Meter And Graduating Cylinder UK
Glass Hydrometer Alcohol Meter 0-96% with Protective Case for Home Brewing Beer
