Setting up a humidor
A humidor is a box with a seal, made to hold cigars at a steady humidity. A new wooden one is dry. If the cigars go in on the first day, the wood takes their moisture. Set the box up before you trust it with anything you mean to smoke.

Where it sits
Keep it in a cool, dry room, out of direct sun and away from a radiator, a sunny window, or an outside wall that bakes in the afternoon. A refrigerator dries cigars out. Do not use one for storage. The practical target, once the box is stable, is about 70°F (21°C) and about 70% relative humidity. Stay under roughly 73°F (23°C). How to hold that, and what to do when the reading wanders, is on Care.
Seasoning
Spanish cedar is the usual lining. It holds humidity, and the cigars pick up a little of its smell. Wipe the bare wood inside, not the humidifier, with a cloth dampened with distilled water. Do not soak it. Standing water stains the wood and can warp the lid. Fill the humidifier (distilled water, not tap water) and close the lid. Leave it a day or two for a small box, longer if the wood was very dry, and read the hygrometer before the cigars go in. Charging that humidifier, including a solution that both gives off moisture and takes it back, is on The humidifier.
A digital hygrometer is easier to trust than an analog dial, which usually needs calibrating. If you have a dial, do not treat the first number you see as the truth.
Putting cigars in
Leave the humidifier's vents clear. Do not pack the box so tight that air cannot move. A box that is about two-thirds full stays steadier than an empty one, because the cigars themselves hold moisture. A cigar that just arrived from a dry shipment can rest a week or two before it smokes the way it will later.
A travel case is a different object. It is for days, not for the cabinet at home. That is on Travel humidors.