If you're driving down the road and you see an emergency vehicle that has it's sirens and lights on you should if possible pull off to the side of the road and let the emergency vehicle get past you and then once the emergency vehicle has gotten past you then you can look to make sure it's clear and pull back onto the road.
If you're sitting at a traffic light that's red and an emergency vehicle is behind you with it's sirens going and lights flashing then if possible pull out into the intersection and turn your steering wheel so that you pull out in front of the car next to you if there's a car next to you.
This should allow enough room for the emergency vehicle to get past you.
If it's not safe to pull out into the intersection at the red light then sit tight and wait for the light to change.
A professional firefighter or ambulance driver or even police officer will wait behind you because they don't want you pulling out into oncoming traffic and getting into an accident yourself causing another emergency.
Emergency vehicle drivers are trained to get around your vehicle if needed by driving over curbs etc.