Creating custom emergency missions?

Hello, so I see videos of people on YouTube who fly missions in MSFS 2024 where they fly an emergency helicopter to the scene of something like a vehicle accident, which appears visually in the game. How can I create my own mission in the sim and have all the objects like emergency vehicles and crashed cars appear in the game? I just want to make my own simple missions to fly.

Thanks

Edited 9 hours ago9 hr by jt233