There is only one version of the Android SDK. Revisions just update some features, such as ADB or the building system for making Android apps. However, you can download more packages in your SDK installation, such as Android 4.3 or Android 2.1. To do that:
Go into the path you downloaded the SDK into. Then open SDK Manager.exe
. When it loads and refreshes the packages list, it will display a list of packages you can download. If you want to download the 4.3 packages, just click the checkbox next to the Android 4.3 - API level 18 item.