How to use different versions of gromacs from the same machine

GROMACS version: 2020.5 and 2019.6
GROMACS modification: Yes/No

I want to use two distinct versions of gromacs on my computer. For specific reasons, I want to use 2020.5 and 2019.6 as well. I installed 2020.5 initially, but realized I also need 2019.6 as well.

In order to run both versions, I need to be able to call them with different names. I want to use the 2019 version with gmx_19 and the 2020.5 version with gmx_20.

To do so, I obtained the 2019.6 version, untarred it and ran the falling script:
The untarred file is in /home/user/software/gmx_19

module purge
module load intel/19.1/64/
module load openmpi/intel-19.0/3.1.3/64
module load cudatoolkit/11.2
module load rh/devtoolset/9

cd gromacs-2019.6
mkdir build
cd gromacs-2019.6/build/
cd …/…


OPTFLAGS="-Ofast -mtune=broadwell"
cmake3 … -DCMAKE_BUILD_TYPE=Release

make -j 8

I believe this will let me call gromacs using gmx_196g. However, when this script runs, I still cannot call gromacs with gmx_196g. I type in gmx_196g -h and it simply says
-bash: gmx_196g: command not found

Can someone advise me on how to run two gmx versions from the same machine?

Each time you wish to use a different version, you need to source the relevant GMXRC file in the bin subdirectory of that installation. That will configure your environment to find and use those executables.

Thank you for your answer @jalemkul! sorry, but what do you mean by source? I see the GMXRC file, do you mean I should execute it so ./GMXRC?

The command is source GMXRC

This is my bin directory:  gmx-completion.bash           GMXRC       GMXRC.csh
    gmx_196g  gmx-completion-gmx_196g.bash  GMXRC.bash  GMXRC.zsh

I did

source GMXRC

I type in gmx_196g -h and I still am getting -bash: gmx_196g: command not found