First download the Android SDK from here.
Extract all the files to your prefered location and open a CMD prompt. Change to following path and type in following command. For example
cd C:\Users\bw\Downloads\android\sdk\tools .\android.bat
Now in the Android SDK Manager you can install all your needed SDKs. Also check the USB Drivers.
If you use fastboot you can now put following path to your PATH variable, so you can use fastboot in your Terminal without type in the whole path.
After that all should work. But for me the USB Drivers don’t work (for fastboot). Download the driver pack from this site and extract it. Now connect your Device in Fastboot Mode and in the Device Manager update the driver and give the location from the driver pack.