The EVAP monitor test is part of the OBD II system and is designed to check for leaks in the vehicle's evaporative emission control system. The test is performed by monitoring the pressure in the fuel tank while the engine is running. If there is a leak, the pressure will drop and the EVAP monitor will fail.
To set your EVAP monitor, you'll need to connect your car to an OBD II scanner and turn on the ignition. The scanner will read the pressure in the fuel tank and then start the engine. Once the engine is running, it will continue to monitor the pressure. If there is a drop in pressure, it will indicate a leak in the system.