Alpha Amylase helps yeast by breaking down long chain sugars and starches that the yeast would normally not be able to digest, allowing for a more complete fermentation, higher ABV, and a cleaner fermented beer.
Just add 1/3 of the packet (5 g) to your mash, then after boiling, adjust your temperature to 185 - 203°F (85 - 95°C) and add the remaining 2/3 of the packet.
Your fermentation will be quicker and more complete, and you'll get a bit more booze out of it!
