First, turn off the water supply to the washing machine or appliance . This is done by tuning the valve off to where the hose attaches to the water supply. If you cannot do this, you can turn off your entire house water supply.
Second, remove the hose from the valve with an adjustable wrench. You will need to loosen the fitting then you can finish taking the hose off by hand.
Third, look at the set up of the valve. You will need to remember this set up or take a picture and go to a local hardware store or plumping supply store to purchase a hammer arrestor. The hammer arrestor will come in many different angles and styles so you will want to choose one that works best for you.
Fourth, attach the hammer arrestor to the valve and tighten it with the wrench.
Fifth, attach the hose to the hammer arrestor and tighten it with the wrench.
Sixth, turn on the water to the appliance or house and check for leaks at the attachment sites.