Unsolved Qt creator can not deploy apk to emulator.

[siaswar]

I can make Hello world program and build it. (qt 5.6, nkd9). I can find *.apk file, so program makes one. but running on emulator cause the problem

Error while building/deploying project App1 (kit: Android for armeabi-v7a (GCC 4.8, Qt 5.6.0))
When executing step "Deploy to Android device"

I drag and drop apk file directly to emulator and it shows a window from apk installer which says installation failed and I should verify adb path settings.
What can I do?
Where is that setting? I searched Qtcreator and emulator many time and did not find anything