How do I figure out how Postgres was installed on my Linux system?
If you are simply looking to start and stop it, and a service or systemctl module doesn't exist on your machine, you can use pg_ctl to start and stop the Postgres server.  You will also need to have the path to the data directory handy (typically, the folder that contains postgresql.conf and pg_hba.conf), and pass that in along with the -D flag:

pg_ctl -D /path/to/data_dir start|stop

If no data directory exists, you will either need further assistance to help you get an existing database cluster up and running, or you can use initdb to create a new database cluster