There are simple and inexpensive ways to darken wood at home, whether with a commercial stain, or with natural products such as coffee or black tea. If you are in the mood for a darker look, it will therefore not be necessary to change any of the wood in the house.
Steps
Method 1 of 3: Using wood stain

Step 1. Prepare your workstation in a well-ventilated location
Cover the floor with a tarp or several newspapers to avoid splashing the floor with stain or wood dust. If you are going to do the procedure indoors, open the windows, and turn on a fan to circulate the air.

Step 2. Sand the wood with a 120 grit sandpaper
Lightly sand the entire surface of the material, always in the direction of the wire. That way you avoid scratching it.

Step 3. To finish this step, pass a 220 grit sandpaper
The finer sandpaper will help to make the surface even and smooth, removing any unevenness that may have been left over from the first hand.

Step 4. With a brush, apply a coat of wood conditioner to the surface
Apply the product, which can be purchased at home and construction stores, one or two hours before using the stain.

Step 5. Open the stain, and mix it well before using it
As you move, scrape the bottom of the can so that any decanted components can mix with the rest.

Step 6. Use a brush or cloth to apply a layer of stain to the wood
Try to do this evenly, always following the direction of the material thread.

Step 7. Allow the product to penetrate the surface for five minutes
If you want it less dark, leave the tin on it for less time.

Step 8. Wipe away excess stain with a cloth
Again, this must be done in the direction of the wire.

Step 9. Allow the stain to dry according to the manufacturer's directions
Read product label for proper waiting time.

Step 10. Apply a polyurethane or lacquer finish to protect the wood
First of all, wipe the surface of the material with a cloth to remove dust and chips.
Method 2 of 3: Staining with Tea and Vinegar

Step 1. Boil half a liter of water
Let it boil until it is time to transfer it.

Step 2. Pour the boiling water into a heat resistant container
Ideally, it should have a large opening, as you will place the brush inside it.

Step 3. Leave two tea bags in the container for 24 hours
Leave them in the water for a full 24 hours, so that it completely darkens.

Step 4. In another container, place a steel wool and half a liter of apple cider vinegar
For best results, use a type 0000 straw. Leave it to soak in vinegar for 24 hours.

Step 5. With a brush, apply the black tea to the wood
Cover the entire surface to be darkened.

Step 6. Let the tea wood rest for an hour
This will allow time for the wood to absorb the tea before applying the stain.

Step 7. Apply the steel wool vinegar mixture to the wood with a brush
As always, follow the wire direction of the material. Cover the entire surface of the wood with the solution to prevent staining. The mixture will make the wood oxidize, and it will start to darken.

Step 8. Let the wood dry for an hour
If it isn't as dark as you want it to be, or if it has stains on the surface, repeat the procedure with the black tea and the vinegar and steel wool solution.
Method 3 of 3: Browning with Coffee
Step 1. In a heat resistant container, place 240 ml of ground coffee

Step 2. Add 300 ml of boiling water
Pour it in slowly so it doesn't sneeze or throw the coffee out.

Step 3. Let the coffee sit for 30 minutes
If the mixture doesn't cool in half an hour, wait a little longer.

Step 4. Place a coffee strainer in a strainer
Place it right in the middle of it.

Step 5. Hold the strainer, and strain the coffee into a container
It should have the opening big enough for you to put a brush inside. Leave the container separate.

Step 6. Prepare the workstation
So as not to make too much of a mess, do it outside. If this is not possible, cover the floor with a tarp.

Step 7. Sand the wood with fine sandpaper
Use a grit sandpaper between 180 and 220. It can be purchased at home and construction stores. Gently sand the wood in the direction of the wire until the surface is smooth.

Step 8. With a brush, apply the black tea to the wood
Avoid exaggerating the amount, or the mixture could puddle on the surface. After covering it, let it dry.

Step 9. Keep applying more layers, until you reach the desired level
Between each application, let the wood dry. When you have finished browning and want to seal the wood, apply a finish with a brush.