This is another one of those things I've done all this several times before, but need to keep looking up the documentation.
To login to PostgreSQL after a fresh installation1 you need to change to the postgres user and run psql (no password needed, it uses Peer Authentication)
sudo -u postgres psql
from there you can create a user and access it as you normally would.
createuser -P -s -e michael
to connect to a database use
\c database_name
to list the tables run
\dt
and to make the output format expanded so it fits on a small screen simply switch
\x on
-
In my case that's usually on Debian or Ubuntu but it should be the same on most Linux distros. ↩