I didn't have to change my prostgresql.conf file but, i did have to do the following based on my psql via command line was connecting and pgAdmin not connecting on RDS with AWS.
I did have my RDS set to Publicly Accessible. I made sure my ACL and security groups were wide open and still problem so, I did the following:
sudo find . -name *.conf
then sudo nano ./data/pg_hba.conf
then added to top of directives in pg_hba.conf file host all all 0.0.0.0/0 md5
and pgAdmin automatically logged me in.
This also worked in pg_hba.conf file
host all all md5
without any IP address and this also worked with my IP address host all all <myip>/32 md5
As a side note, my RDS was in my default VPC. I had an identical RDS instance in my non-default VPC with identical security group, ACL and security group settings to my default VPC and I could not get it to work. Not sure why but, that's for another day.