Three steps.
All day.

Start with clean skin. The mineral works by creating an environment where bacteria cannot grow, so you must start with a clean slate. Applying over existing bacteria won't remove existing odor.

Run the deodorant stone under cool water for two seconds, or apply to wet skin immediately after showering. The moisture allows a microscopic layer of the salt to dissolve onto your skin.

Apply broadly to the underarm area for 15-30 seconds. Be thorough. The film is invisible, dries quickly, and will not transfer to or stain clothing.