How to connect to postgresql with correct username and dbname?

I am trying to replicate the Bike Rental Shop on my onw server but I can’t make the script understand how to read my data from the batabase:
ex: on the course we learned to set the PSQL variable like:
PSQL=“psql -X --username=*** --dbname=*** --tuples-only -c”
What are the settings I sould use to set a dbname and a username so my installed postgresql could understand it?

the error message I receive when I try to insert something into the database:
psql: error: connection to server on socket “/var/run/postgresql/.s.PGSQL.5432” failed: FATAL: Peer authentication failed for user “****”

Your code so far

PSQL=“psql -X --username=*** --dbname=*** --tuples-only -c”

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Challenge: Learn Bash and SQL by Building a Bike Rental Shop - Build a Bike Rental Shop

Link to the challenge:

Faced the same issue when I tried to replicate those projects locally. This one helped me out:

Basically you just need to install it first and set it up before.