Locate and Read the Main Circuit Breaker or Fuse Block
Make sure the floor around the main service panel is dry, then open the metal door on the service panel. Inside the panel, you will see two rows of individual circuit breakers with small toggle levers. These individual circuit breakers are numbered, and they control individual branch circuits running through your home. The amperage of these breakers will be between 15 and 50 amps, usually.
At the top end of the two rows of branch circuit breakers, there will be a central circuit breaker that controls the power to the entire panel. This is the main circuit breaker, and its amperage rating will something like 60, 100, 150, or 200 amps. In rare instances, the main circuit breaker may be mounted at the bottom of the service panel. The main circuit breaker may be bolted in place, or it may be a snap-in breaker similar to those serving branch circuits.