Place the sized socket on your wrench and if possible attach a wrench extender to reach the nut.
By putting the wrench on the nut on the negative terminal turn it clockwise to loosen.
Pull the negative connector from the battery and push it aside to avoid contact with the battery as you are working.
Repeat the same procedure to disconnect the positive terminals and do not let the positive connector touch any metallic part of the car, this may damage or disrupt the circuits in the vehicle because of residual current in the system.
Carry on with whatever you are doing. Remember when the battery cables are disconnected, you can do repairs on electrical components safely.
Simple Steps to follow while putting a new car battery
Disconnect the battery then unscrew the brackets holding it in its tray.
Car batteries are heavy so lift the battery up, out of its tray with care
Use diluted baking soda mixture with old toothbrush to brush the tray and connectors.
Do not put the new battery before they dry
Put the new battery on the tray and tighten the clamps.
Connect the cable for the positive terminal should be connected first followed by the negative one. Don’t forget to tighten securely tighten the nuts on each.
Close the hood then start the car.
Old battery should be disposed of properly. Inform the auto parts store where you purchased the new battery from to come and pick it. You can also take it to an automotive garage at some fee. Recycling centers also do accept old batteries.