Before you can SSH into a Docker container, you need to know the name of the container.
Run
$ docker ps
to list the currently running containers and find the name of the one you want to connect to. If you don't see the one you are looking for, it may not be running.
Then, you can connect to it by name with a bash session like so:
$ docker exec -it <container name> /bin/bash
The
-it
flags open an interactive emulated terminal connection. /bin/bash
is the
command that gets run in that context.