I just got a free refractometer.........big question how do I use it for brewing?

do you have promash or beersmith? they have refractometer utils. There's also smartphone brewing apps that have it (like brewzor).

basically it's converting brix to SG

I have beersmith1 I did not think to look there.

You really don't need those. If it's got ATC, just apply a drop of unfermented wort (hot or cold) on the lens and quickly close the cover. Wait about 15 seconds and read by pointing it at a light source. The brix reading is ABOUT 1/4 of the gravity, IE a brix of 15 is about 1.060. The above mentioned calculators will get you closer.

To calibrate it, put a drop of distilled water on the lens and using a screwdriver, adjust for 0.

If you have an Android platform smartphone, search for the Brewzor Calculator app, good stuff and very user friendly, is free and has alot more features than I use.

Gee, I have one from when I was doing marine aquariums (that was an abismal failure and you can't drink it). I've never thought about using it.

Also, be aware that using it after the beer has been fermenting requires a correction for the alcohol in the beer. The most accurate spreadsheet for correcting is http://seanterrill.com/2011/04/07/refractometer-fg-results/ .

Do yourself a favor and just use it with unfermented wort. The fact that you only need a drop of boiling wort is, in and of itself, a worthwhile feature.

Good recommendation. Although I don't use mine any more even pre fermentation. It went crazy and just won't calibrate correctly. Using a metal cocktail shaker and a bowl of ice water I can cool a boiling sample down to 60F in less than a minute, so I do that and use my hydrometer.