If you use docker-compose and community edition:
Now since on dockerhub latest points to 8.0.3 it should only be
docker-compose down docker-compose up -d
the latest release should be taken from dockerhub (as far as i understand docker). If that does not work, you can change the image line for seafile-mc like i described above.
If you also wish to enable elastic search you have to add the elastic search component to your docker-compose.yaml file like described in the pro docker-compose file and also edit/add the seafevents.conf config file like described here and restart the container again.