In order for this build this image properly, you need to download WordPress (or take an existing install) and copy wp-content into this directory, renaming it to just content - discard/ignore the WordPress core as it's being downloaded within the image itself.
Next, create two directories named db and redis and leave them empty. They will be used to store MySQL and Redis database files.
Finally, to build the image, run:
$ docker-compose build
And then to run the container, use this command:
$ docker-compose up
(cancel these with CTRL + C)
To test it out, open your browser, and navigate to http://localhost:8080 (or whatever you have set in the .env file)