Gather 1 Water Bottle
Gather 1 Nether Wart
Gather 1 Glistering Melon Slice
Gather 1 Brewing Stand
Gather Blaze Powder for fuel
Place the Water Bottle in the Brewing Stand
Add Nether Wart to make an Awkward Potion
Add Glistering Melon Slice to make a Potion of Healing
Use Redstone to make it a Potion of Healing II if desired
Use Gunpowder to make it a Splash Potion of Healing if desired