Required (Windows):

1. Download and install Universal ADB Drivers: https://github.com/koush/UniversalAdbDriver or http://adbdriver.com/downloads/
2. Download and install minimal ADB + Fastboot installation: http://forum.xda-developers.com/showthread.php?t=2317790
3. Open windows command prompt and go to folder when adb is installed - if in doubt SHIFT + right click on a folder containing newly installed adb.exe and select "Open command window here".

Now there are easy way and hard way. Easy first: