Compiere_253a.tar.gz has been downloaded for the purposes of this manual:

http://www.compiere.org/download/index.html

After downloading, un-extract Compiere to your preferred location.

Enter the /opt/ directory

$ cd /opt/

and type following command:

$ tar xvfz Compiere_253a.tar.gz

The Compiere directory is now available on /opt/Compiere2