Confusion on connecting to postgre

Chicken before Egg or vice versa/
So, I couldn't connect to a running postgre installation after many tries with Metabase installed in a docker volume at

so today I deleted my running postgresql, mysql, redis containers.

Fresh start to make sure they were installed via docker.
Now I have new postgresql, mysql, redis installations.
But they have no tables and I don't know yet if the are running.

postgre shows up here :/var/lib/postgresql/data

I saw this but how do I contact and configure database installations I just created? --

docker run -d -p 3000:3000
-e "MB_DB_TYPE=postgres"
-e "MB_DB_DBNAME=metabaseappdb"
-e "MB_DB_PORT=5432"
-e "MB_DB_HOST="
--name metabase metabase/metabase

This has been the most frustrating, hours consuming process trying to use Metabase. It is the first data app I've installed in my various linodes volumes that did not connect when I had named database servers, let alone with my new ones today.

How do I get past this point to demo Metabase?

Is the postgres in the same server? or an external server? you have to put the hostname of the postgres on MB_DB_HOST.

If you are going to demo metabase, just use the embedded h2 database and know the limitations it has. Otherwise use our cloud trial for 15 days.

BTW: redis is not needed, and you only need 1 app db if you're going that way (postgres or mysql)

At my volume no matter how I've installed postgresql at root or in docker container by latest docker instructions I can't get Metabase to discover the database. Even when terminal shows the postgresql running and it is connected to host ip.

HOWEVER Metabase has no problem when I put in the configuration to remotely access a mysql database at a completely different hosting service on another website of mine.