Clean the interior of the humidor using a sponge that is damp with distilled water. Wipe all of the panels inside the humidor and pay special attention to the cracks and seams.
Fill the humidifier within the humidor with distilled water. Close the humidor for several hours. This will allow moisture to penetrate the wood inside.
Open the humidor and wipe it down with a damp sponge a second time. Ensure that the humidification unit is full and close the humidor for several more hours. Repeat this step two additional times.
Open the humidor and fill the humidification unit with distilled water. Close the humidor and check the humidity level using a hygrometer several times a week, adding water to the humidification unit as necessary. A hygrometer is a meter that is designed to measure humidity. At about the three- to four-week mark, the humidor will stop absorbing additional water and will have a stable humidity level.