ok, here's how it worked:
I downloaded the Adt bundle and Copied the file "SDK Manager.exe" to the Android studio root directory and just executed it (this set the SDK environment variable to C:\Program Files\Android\android-studio\sdk).
then In Android studio clicked Configure ==> Project Defaults ==> Project Structure（Or File==> Project Structure)
then in the tab Project / Project SDK selected android SDK.
then in the tab SDKs / build target selected Android 4.2.2