Step 1: Stop the water
Every fixture has a local stop — a small valve under the sink or behind the toilet. If the leak is inside a wall, at a water heater, or under a slab, go to the main shutoff instead. In Tupelo-area homes the main is usually where the service line enters the house, at the meter box near the street, or in a crawl space near the front wall.
Find and label that valve before you ever need it. In an actual emergency, nobody wants to be learning the layout with a flashlight.