Buy some dog shampoo.

Fill the bath/sink up with some water. Not too hot and not too cold. Fill the bath up to a suitable level for your dog.

Put some dog shampoo into the running water.

Lift the dog into the bath/sink.

Rinse the dog with warm water.

Apply dog shampoo onto the dog with a cloth.

Massage the shampoo into the the dogs hair.

rinse off the shampoo with warm water, you can use a shower head or a cup and water.

repeat step 7 & 8

Lift the dog out of the bath/sink using a towel.

Dry the dog off with a towel or hair dryer.

give the dog a treat and tell him/she they are a good dog.