I don't know much about bitcoin docker but I found some useful links.
Can you post the source here where did you pull this image? If you get it from docker hub it should include the guide.
Can you check this it includes the guide
https://hub.docker.com/r/kylemanna/bitcoindAnd can you clarify this "i cannot access it from outside the container" are you trying some RPC calls? or you are trying some command line without docker?
If you are trying some RPC calls and didn't work you need to set up the config first check this link
https://github.com/kylemanna/docker-bitcoind/blob/master/docs/config.md