Can anyone advice me on how to set the environment variable FREESURFER_HOME for installing it in OS X 10.6.8 (with XQuartz installed)?

My directory for Freesurfer: /Applications/freesurfer

I know I also have to add:

setenv FREESURFER_HOME /Applications/freesurfer

source $FREESURFER_HOME/SetUpFreeSurfer.csh

But I am not sure where exactly I should add these lines.

Do I need to edit the .csh file in Freesurfer.

How should I do this? using Text Edit from apple would work?

Thanks,

Pablo