How to automatically run an emulator in "React-Native"

Question

• In Desktop

  (The emulator turns on automatically)

npm start video

terminal(?) image

emulator image

• On the laptop After turning on the emulator can activate the React-Native

  Which program is the terminal image among the images?

  (Powershell X, Azure X, cmd X, ...)

I want to use it like a desktop

• case of me

• What went wrong: Execution failed for task ':app:installDebug'.

com.android.builder.testing.api.DeviceException: No connected devices!

Why do you press "DownButton" when you didn't explain it to me? If there is a lack of explanation, which part is it? (It may be because of my English skills.)