Paste the application (.apk file) in to SDK/Platform-tools folder.

and also run the below command in cmd prompt.

adb install ApiDemos-debug.apk

Getting below error message, It shows waiting for device but after 2-3 hours, its still showing same message.

D:\SDK\platform-tools>adb install ApiDemos-debug.apk
error: device unauthorized.
This adb server’s $ADB_VENDOR_KEYS is not set
Try ‘adb kill-server’ if that seems wrong.
Otherwise check for a confirmation dialog on your device.
adb: error: failed to get feature set: device unauthorized.
This adb server’s $ADB_VENDOR_KEYS is not set
Try ‘adb kill-server’ if that seems wrong.
Otherwise check for a confirmation dialog on your device.

• waiting for device -

But i checked devices connected or not via below command,

The device(Android simulator) was successfully connected.

D:\SDK\platform-tools>adb devices
List of devices attached
emulator-5554 unauthorized

Kindly help me, how to fix this error.