Changing user when running psql command on Mac terminal

Question

I installed PostgreSQL on my Mac (from their website) and set it up to have it run on my terminal using psql command. However, when I use psql command, it asks for password for my Mac user and when I enter the password, it returns password authentication error. I only have postgres set up as a user. When I run psql -U postgres and enter the password, I am connected to the database.

How can I change the default user to postgres instead of my Mac user (jp) so I can just use psql command? I have also included what I have in .bash_profile file.