See the MPICH project page. To use MPICH, you’ll use the module tool.

You can see what versions are available by using:

[me@login01 ~]$ module avail mpich

------------------------------ /opt/modulefiles -------------------------------
   mpich/3.3.1-gcc-8.3.1

Use "module spider" to find all possible modules and extensions.
Use "module keyword key1 key2 ..." to search for all possible modules matching
any of the "keys".

To load a specific version, you would use:

[me@login01 ~]$ module load mpich/3.3.1-gcc-8.3.1

while the "mpich" wildcard will load the default version, mpich-3.3.1-gcc-8.3.1 in this case.

You should now be able to run MPICH commands:

[me@login01 ~]$ mpicc --version

gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5)
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.