Having a regular cleaning routine in place is key to maintaining your katana. 

You can purchase a traditional sword cleaning kit that will have everything you need. There are three steps: removing oil, polishing the blade, and oiling the blade. 

Using a sheet of rice paper from the kit or soft cotton cloth, remove any oil that is still on the blade from the previous maintenance. Take the powder ball and tap it lightly against the blade about every two inches or so along its length. Take a fresh piece of rice paper and rub the powder over the blade to polish it. Do this until both sides of the blade have been polished and the powder completely removed. Take the bottle of oil and apply a few drops along the length of the blade on each side. Use a fresh piece of rice paper to spread the oil evenly on the blade.