Unable to launch emulator

Hi all, I am new to Expo. I have been editing my code using Sublime. I wanted to debug my app using emulator but I not sure how do I create an emulator.

When I selected the ‘Open in Android’ from Expo, it shows me these error messages:

Couldn’t start project on Android: Error running adb: No Android device found. Please connect a device and follow the instructions here to enable USB debugging:
Cómo ejecutar apps en un dispositivo de hardware  |  Desarrolladores de Android  |  Android Developers. If you are using Genymotion go to Settings → ADB, select “Use custom Android SDK tools”, and point it at your Android SDK directory.

Any ideas? Thanks in advanced!

hi-

Did you follow the instructions in the error message?
Did doing that work?

Hi, yes I installed the genymotion and Oracle virtual box. I followed the guideline to choose Nexus 5 as virtual device on genymotion, but upon launching the virtual device, it told me virtualBox cannot start virtual device.

my emulator isnt running . keeps giving me error messages.