How to Reference a Library in your Project

1. Create or open your Android project.

2. Ensure the Google Play services SDK is installed. It is located in the last folder called Extras.

3. Import the Google Play services library.

4. In the Package Explorer, right-click on your project name, and select Properties from the pop-up menu, or even easier, select your project name and press Alt-Enter.

5. Select Android from the list on the left.

6. Scroll to the bottom to the Library section. Click on the library you'd like to reference to select it then click OK.

Resources:
http://developer.android.com/tools/projects/projects-eclipse.html#ReferencingLibraryProject