// Option A //

To download Yahoo! Messenger Plug-in mod from HappyMod.com.
You need enable the option "Unknown Sources".
1. Click on the above link to download Yahoo! Messenger Plug-in mod APK.
2. Save the file in your device Downloads folder.
3. Now tap on Install and wait for the installation to finish.
4. Once it is done, open the game and start playing it right away.

// Option B //

To download Yahoo! Messenger Plug-in from HappyMod APP, you can follow this:
1. Open your browser and download the HappyMod APK file from HappyMod.com - the only official website of HappyMod.
2. Open Android Settings and go into Privacy or Security.
3. Tap the option to Allow Unknown Sources and enable it.
4. Go to your Android downloads and tap the APK file.
5. Follow the directions on the screen to install it.
6. Search Yahoo! Messenger Plug-in in HappyMod App.