You can enable a Redis password using the cli:

root@97d66c2097c3:/data# redis-cli
127.0.0.1:6379> CONFIG SET requirepass <PASSWORD>
OK

Next time you try to use the Redis cli you will need to auth:

root@97d66c2097c3:/data# redis-cli
127.0.0.1:6379> AUTH <PASSWORD>

To disable the password:

CONFIG SET requirepass ""