Once you are finish with installation of Android SDK you can install Android SDK packages.
If you are working with Appium or any testing tool, in order to create Android emulators for testing, It is required to have few packages installed on the system.
This can be achieved using Android SDK manager.
Follow below steps:
Step 1: Launch you Android Application
Step 2: Select Android SDK from Configure.
Step 3: Select up to last 3 version, In my case I am selecting up to Android 6 (Marshmallow) and click OK.
Step 4: A popup will appear that following component will be installed, click OK again.
Step 5: Accept the Licence and Click Next.
Step 6: Download and installation will start. This will take some time.
Step 7: Click Finish once installation done.