android studio - manually download system image for emulator

In windows: First locate your android-sdk. By default it's in your C:\Users\Your.name\AppData\Local\ in it's root folder. where you can find: SDK Manager.exe, make a folder name it "system-images", my api 25 image is at system-images\android-25\google_apis\x86_64\Files

Hope you can Figure it out. Comment if you have any problem.

In mac OSX:

~/Library/Android/sdk/system-images/android-[API_VERSION]/[API_TYPE]/x86

Replace [API_VERSION] with Android version you are downloading and the [API_TYPE] can either be google_apis_playstore or google_apis depending on whether the image you are downloading comes with Google Play or not.