Copy .env_example and save it as .env, edit as you like
% docker-compose pull
Pulling strapiexample ... done
Pulling mongoexample ... done
% docker-compose up -d
Creating network "strapi-docker-composer-example_strapi-app-network" with driver "bridge"
Creating volume "strapi-docker-composer-example_strapidata" with default driver
Creating strapiexample ... done
Creating mongoexample ... done
https://strapi.io/blog/how-to-run-a-strapi-dev-stack-with-docker-compose