To support a given application, you often create a new role and database to match.

The shell commands to run would be these:

$ createuser -P blogger
Enter password for the new role: ********
Enter it again: ********

$ createdb -O blogger blogger

This assumes that pg_hba.conf has been properly configured, which probably looks like this:

# TYPE  DATABASE        USER            ADDRESS                 METHOD
host    sameuser        all             localhost               md5
local   sameuser        all                                     md5