Zend certified PHP/Magento developer

How do I install pgaudit on PostgreSQL 11.5 in Red Hat Linux environment?

PostgreSQL 11.5 was installed with Control-M in a Red Hat Linux environment. Unfortunately, there are only 2 extensions (dblink, plpgsql) that were a part of that installation.

I am new to PostgreSQL. So I have researched ways to install pgaudit and nothing seems clear and nothing seems to work. I am hoping an expert can provide clear instructions.

Based on research I downloaded pgaudit-1.3.4.tar.gz which is supposed to work with PostgreSQL 11.5

Then I run the following command from GitHub:

make install USE_PGXS=1 PG_CONFIG=/opt/app/product/cm/pgsql/bin/pg_config
gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -O2 -fPIC -I. -I./ -I/opt/app/product/cm/pgsql/include/server -I/opt/app/product/cm/pgsql/include/internal  -D_GNU_SOURCE   -c -o pgaudit.o pgaudit.c
pgaudit.c:11:22: fatal error: postgres.h: No such file or directory
 #include "postgres.h"
                      ^
compilation terminated.
make: *** [pgaudit.o] Error 1

As you can see I get an error about a missing postgres.h file. I believe postgres.h is a header file. But I can’t find instructions to install header files.

I don’t understand why this is complicated and why I can’t find the right file to install. Could someone provide the correct instructions?