finding the path to start postgres
When you install a program in Linux it is most often configured to just work. So you would do service postgresql start to start it, service postgresql stop to stop, and service postgresql status to check if it's working etc.

You may need to set it up that it will start automatically on boot. How to do this depends on your system version, so you may need to Google it. On my system it is chkconfig postgresql on to enable, and chkconfig postgresql off to disable.

If you want to find where is data directory of a running postgres then you can use sudo su postgres -c "psql -c 'show data_directory'". You can find Postgres configuration files, logs and data there.