how to path

Make folder, example in $HOME/.opengrads:
$ mkdir -p .opengrads

Download file from web below and paste at $HOME/.opengrads:
https://sourceforge.net/projects/opengrads/files/grads2/2.2.1.oga.1/Linux%20%2864%20Bits%29/opengrads-2.2.1.oga.1-bundle-x86_64-pc-linux-gnu-glibc_2.17.tar.gz/download

Extract use bash or anything:
$tar -xzvf opengrads-2.2.1.oga.1-bundle-x86_64-pc-linux-gnu-glibc_2.17.tar.gz

Go to Contents folder:
$cd opengrads-2.2.1.oga.1/Contents

Path some file (bufrscan,grib2scan,gribmap,gribscan,opengrads,stnmap) to /usr/local/bin
Example for 'bufrscan', and do to the other:
$sudo ln -s bufrscan /usr/local/bin

Test to open 'opengrads', if can be open and process '.ctl' or '.nc' file, thats work