Most water shut-off valves are located outdoors near the front of the house. Look for a hose bib, it’s an outdoor water spigot where you could attach a garden hose. It might come up from the ground close to a wall of your house. Older models have a round on/off handle (valve), while newer ones have straight handles.
Turn the valve to the “off” position, and then go inside and turn on a water faucet. If water comes out, try turning the outdoor valve in the opposite direction. If that doesn’t shut the water off, or if the valve breaks when you turn it or if you can’t find it, call a plumber right away to resolve the problem now rather than waiting until you have an emergency at home.
That outdoor valve will shut the water off to your entire home, and you only need to do that during an emergency. If you’re repairing a faucet, a toilet or the washing machine, you’ll find shut-off valves under the sink or on the wall nearby that will kill the water supply just for that area. Usually, you don’t need to turn off all of the water in the house to make simple repairs.