Publishing an APK

I currently have the Android License for Unity and I am trying to publish a project for some play testing. However, I cannot for the life of me figure out how to publish the APK. I know to go to “build” but it open a new window and asks for select “android SDK root folder” I don’t know what this means.

Thanks.

Well for some reason I cannot get the JDK to install which is required for Android SDK. Just a lot of round about right now, but thank you