You want to know how strong your moonshine is, both for aging and as an indication of how well your distillation went. Be sure not to confuse the proof and tralle readings on the hydrometer. Your proof will always be two times the amount of the tralle. If you do decide to age your whiskey, you want it to go into the barrel at around 58% to 70% ABV. Aging will make the whiskey smoother and give it its distinctive taste. Whiskey will only age in barrels. When it is bottled, whiskey will stop aging.  Whiskey is generally aged in oak barrels. The barrels can be carefully charred or toasted first, or can be sourced from another distiller that's kept another spirit in the barrel for added flavor. If you want to add oak flavor to your moonshine but don't want to have to spring for a barrel, you can also add toasted oak chips to your whiskey. Toast your oak chips over low heat (200º F) in the oven for an hour, until they are aromatic but not yet charred. Remove and cool. Transfer to whiskey container and steep for  5 - 15 days or longer, depending on your tastes. Strain the whiskey through cheesecloth or a clean pillowcase to catch all the wood chips. . After your whiskey is aged, you'll want to dilute it before you drink it and bottle it. At this point, the whiskey is still probably 60% - 80% ABV, which would make for a fiery, uncomfortable drinking experience. It should be diluted to around 40% or 45% ABV for a much more pleasant drinking experience. Bottle your whiskey, along with a note on when you bottled it. Always drink responsibly.

Summary:
Use a proof and tralle hydrometer to test the ABV (alcohol by volume) of your moonshine. Age the whiskey. Dilute the whiskey Bottle and enjoy!