WARNING: This process involves editing the registry if you haven't installed another Add-in before
1. Install Windows Live Messenger if it isn't already installed (http://messenger.live.com/)
2. Open the Run Box and type regedit and then press enter
3. Navigate to key HKEY_CURRENT_USER\Software\Microsoft\MSNMessenger (if you dont know how to do this stop at this point)
4. Edit or add the DWORD Key AddInFeatureEnabled and set the value to 1
5. Restart Messenger
6. Click Add-ins in the Messenger Options Dialog
7. Click Add to Messenger and Navigate to the Add-in and click Open.
You are now finished!