Brewing all-grain is much easier than most people think. It basically involves two additional steps: Mashing and Sparging. After these two steps are completed, the boiling process is exactly the same as when extract brewing.
All-grain brewing has the added benefit of improving your brew's quality, composition and consistency.
Mashing: When starches are converted to sugars.
The simplest way to mash is by the single-infusion method. Mashing starts with bringing your brewing liquor (water) to a temperature that will activate enzymes within the grain when it is added. This temperature will typically be in the 156 ºF to 168 º F range. When the grain is added to the brewing liquor, the temperature will drop 8 to ten degrees, bringing the mash temperature down to 148 to 158 degrees. This is the temperature that a saccharification rest should occur at. This is when the sugars are extracted from the grains. Depending on the recipe, this oatmeal-like mixture will sit at this temperature for sixty to ninety minutes.
Sparging: When the sweet wort is rinsed from the crushed grains.
This is accomplished by sprinkling 170 ºF water over the mash and allowing it to seep through. This dissolves the sugar into solution, and it is then carried to the bottom of the mash tun, where it exits through the outlet valve and into your boiling kettle. The easiest way to do this is with a sparge arm. A sparge arm allows you to sprinkle the hot liquor evenly and constantly over the mash, which will yield higher extraction rates than sparging without a sparge arm.
Boiling: Simply brew as you did before.
When brewing all-grain, you will collect and boil 6 to 7 gallons of wort for a five gallon batch. As mentioned earlier, you may need to purchase a larger boiling kettle to do this. Other than this, the process is exactly the same as brewing an extract batch. Add your bittering hops, boil for an hour, and make any other additions as called for in your recipe. Cool the wort and pitch the yeast.