Then, begin by following the directions at https://github.com/atech/postal/wiki/Installation#initialize-database--assets.
Postal can be accessed by checking the section below. Note that "intialize-config" is already run for you, as the database parameters need to be configured before the postal tool can be used.
After configuration is done, run the following to bring the container up.
Be sure to do some port mappings to allow your SMTP server and HTTP(s) server to be accessed. I suggest simply port mapping the SMTP server and using [jwilder/nginx-proxy](https://github.com/jwilder/nginx-proxy) to proxy the HTTP server.