The Armorer’s Cookbook is an item that will give you various recipes for food that can be consumed by the character, but there are also enchant recipes that you can use to enchant your weapons with fire. The Cookbook can be found in a camp in Limgrave. I will show you the exact location of the Armorer’s Cookbook in Elden Ring,
Armorer’s Cookbook Location (Craft Fire Weapon Enchantment) – Elden Ring
In order to collect this amazing item, head out to Limgrave and continue going east from the Gatefront ruins. On your way you will spot a camp that is barricaded with sharp ended poles, inside the camp you will see a few enemies that will try to kill you.
You can either sprint through the enemies and grab the Cookbook that is held by a dead corpse, or kill them all and then collect the item. The Cookbook itself can be found on the right side of the camp once you enter.
To craft your weapon with the fire enchantment, you will need to have the Crafting Kit.
Once all that is done, collect 1 Root Resin, 1 Smoldering Butterfly, and 1 String so you can craft the Drawstring Fire Grease. Which is the fire enchant for your weapons.