In most cases, you can update your ADT plug-in simply as follows:
1. Navigate to Help -> Check for Updates.
2. If there are any ADT updates available, they will be presented. Simply select them and choose Install.
Sometimes a plug-in upgrade may be so significant that the dynamic update mechanism can’t be used. In those cases you may have to remove the previous plug-in completely before installing the newer version.
If You dont know how to install The ADT You can visit this article :
Installing Android ADT Plugin For Eclipse
