Download the antechamber package antechamber-1.x.tar.gz Read the License , note that both antechamber and tleap codes are provided under the GNU General Public Library, Version 2. Use 'gunzip' to uncompress and then use 'tar xvf' to unpack the antechamber-1.x.tar.gz file. Set up the ACHOME environment variable to point to where the antechamber package resides on your machine, for example setenv ACHOME /usr/local/antechamber-1.x set path=($ACHOME/bin $path) This is a sample .cshrc file Go to the $ACHOME and type "make" to install antechamber package