GrADS Software can be found in the link below
http://www.iges.org/grads/downloads.html
You want  the CentOS download under version 2.0.2. 
CentOS5.8-x86_64i686 (a.k.a. RHEL5)
from your home directory

[home ~]$ cd WRF/packages/bin
[home bin]$ wget ftp://cola.gmu.edu/grads/2.0/grads-2.0.2-bin-i686-pc-linux-gnu.tar.gz
[home bin]$ tar -xvzf grads-2.0.2-bin-i686-pc-linux-gnu.tar.gz

You also want to download the data2.tar.gz under the Supplementary Files section.

[home bin]$ cd ../lib
[home lib]$ wget ftp://cola.gmu.edu/grads/data2.tar.gz
[home lib]$ tar -xvzf data2.tar.gz
[home lib]$ cd ~
[home ~ ]$ vi .bashrc
paste this below the last export line
export GADDIR=/home/jmace/WRF/packages/lib
Save & exit
[home ~ ]$ export GADDIR=/home/jmace/WRF/packages/lib
Finished