Easiest way is:
Create an empty Android Application project in your Eclipse workspace.
Copy files in ShowcaseView/library/ folder of github to your new project base folder.
Refresh project in Eclipse.
Goto project properties - Android and select "Is Library"
Clean unnecessary stuff and build.
It should be ready to add as dependency of your app.
Alternatively you can pick another library project .project file and copy it inside this library folder, edit it to match your new project name, etc... And then import in Eclipse. But this is more hardcore if you don't know what you're doing.