How do I use mixed reality apps in Windows 10?

The Windows 10 Creators Update has brought us a whole bunch of new tools, including a simulator that lets you experience mixed reality apps without having an actual headset. Unlike the Hololens emulator that runs apps in a virtual machine, mixed reality apps run just like any other app; the simulator makes them think you actually have a headset, and your movements are controlled with your normal peripherals instead of having your body tracked in real time.
Ready to check out mixed reality on your PC? Here's how to set up and use the Windows Mixed Reality (WMR) simulator in Windows 10 Creators Update.