Once your containers are up and running, get into one of the nodes by running:
sudo docker exec -it scylla-node1 cqlsh
This will enter into the container node and get into the cqlsh
space.
Once there, you can run some commands:
DESC keyspaces
DESC catalog
DESC catalog.mutant_data
SELECT * FROM catalog.mutant_data;
And of course you can run basically any other CQL command.