You can follow instruction in the following link, it not only just helps you update xtext Library
but also other libraries too.
Here is the link Ref Link
Install Pre-Configured Eclipse With Xtext
- Go to http://xtext.itemis.com and select the distribution that matches your OS.
- Unzip the archive into the directory of your choice. Windows Users should choose a directory close to the root since the zip contains a deeply nested folder structure. The maximum path length on windows may not exceed roughly 256 characters.
- Launch Eclipse and select the workspace location. It is basically the location for your user data and project files and may be an empty directory.
Install Xtext From Update Site
If you have no existing Eclipse installed, it is probably easier to choose a pre-configured Eclipse. Alternatively, you can go to http://www.eclipse.org and choose the Eclipse IDE for Java Developers. Find the download link that matches your platform and follow the installation instructions above to extract and launch Eclipse.
- Choose Help -> Install New Software... from the menu bar and Add... the following update site: http://download.itemis.de/updates/. This site aggregates all the necessary and optional components of Xtext.
- Select the Xtext SDK from the TMF Xtext category and hit Next until you can Finish the wizard.
- After a quick download and a restart of Eclipse, Xtext is ready to use.
IF you are planning to use first method, here is the Download Link to get Xtext 2.4 or later version.