If you have deleted PostgreSQL you will need to re-install it.
If you're restoring from a backup then you don't need the exact same version of PostgreSQL so you can install our currently recommended version which is 9.6.
You can download PostgreSQL from
here.
Be sure to get the correct version for your operating system.
When you install, set the port number to 5432 (it should default to that), and the password to 'dbpass'.