Obtain a steam cleaner. Steam cleaners can be bought or rented from department stores, cleaning supply retailers or home improvement stores. Handheld or portable models as well as bigger models with more attachments are available.
Read the manufacturer's instructions that came with the model. Different steam cleaning units will have differing instructions. Getting instruction on how the unit works and knowledge of all accessories before use will ensure that the unit is used to the best of its capabilities without mishap or injury.
Fill the unit's water tank with water up to the fill line. Some units will have a removable water compartment, which are filled and replaced, and others will be built in, in which case the water will be poured into a large container and emptied into the unit until the holding capacity has been reached.
Attach any extensions or nozzles to the unit. Steam cleaners come with several accessories that aid in cleaning different surfaces, such as extensions with brushes for upholstery and extension hoses and wands for longer reach and larger surface cleaning. Wooden furniture may require a different extension than fabric or upholstery needs. Refer to the operation manual if unsure before proceeding.
Plug in the unit and power it on, allowing the water to heat up. Heating time may differ with each unit, but most are ready for use within five minutes.
Hold the unit or extended wand over the surface of the furniture, about three inches away from the surface if using direct steam for, say, a wooden piece or directly on the furniture for fabric. Go over the entire surface area in an up-and-down motion as if vacuuming the furniture. Continue this until the entire surface area of the furniture has been gone over with the steamer. Change attachments as necessary for furniture with more than one kind of material -- i.e., furniture with wooden or metal legs and arms that has fabric seats and backrests.
Turn off and/or unplug the unit, and allow it to cool for five minutes before removing the water tank and emptying of water. Allow the furniture to air-dry.