This android Documentation says that installation procedure of android Lollipop.
in third step they says that
Select everything under the Android L Developer Preview section and click Install packages.
But I unable to find any section like
android L developer preview. Where to download it I follow all the steps from my eclipse juno.
Before installing latest tools in SDK manager, I would recommend you to update ADT plugin from Help -> Check for updates. Otherwise you would have to face issue described here: Update Eclipse with Android development tools v. 23
As mentioned in 2nd step, first you have to install latest SDK Tools, Platform-tools, and Build-tools.
After installing latest tools, you will get Android L and Android 4.4W sections:
Update all the SDK tools and restart the SDK manager for the Android L sections to show up.
Since now the Android lollipop came try to install and explore from u can download from android site. Api 21
Here u can find guide also for setup: