I have Xamarin Studio, and I need to specify the Android SDK Location. I have previously had Xamarin Studio working on my pc, and for some reason, I need to enter this again
Update v3.3
Update:
Android Studio 3.1 update, some of the icon images have changed. Click this icon in Android Studio.
Original:
Click this icon in Android Studio for the Android SDK manager
And your Android SDK Location will be here