Permission's question

Hi, I am new to Postgres so please bear with me.

How do you create a database where only the owner can read and write to
it. I created a database owned by a user but I noticed that when logined
in as another user that was not an owner of that database that they
could write to it. So my question is that when creating databases, is
there a way to deny everyone except for the owner? Is this something
that would be done in the pg_hba.conf. Is there a way to specify
permissions on an entire database?

If I overlooked something in the manual, please send me the link. Thank you.

- Ryan