I'm having trouble understanding how to view my docker container via my droplet IP

I’m simply trying to view my app in a browser via the IP address. I’m new to docker. I’ve spent a fair amount of time today trying to figure this out, but need a little help.

I have a docker container locally running a silverstripe app. Ive set this container up on a droplet using the marketplace/docker image. The app seems to all be setup and running as it should.

I have a docker-compose.yml file - the top looks like this:

version: "3.5"
services:
  myname-www:
    build:
      context: .docker/www
      dockerfile: Dockerfile
    container_name: myname-www
    ports:
      - "${WWW_HTTP_PORT}:80"
      - "${WWW_HTTPS_PORT}:443"

this is sitting in the project folder: /var/myname

and in an .env file I have these lines:

# Docker Configuration
WWW_HTTP_PORT=2375
WWW_HTTPS_PORT=2376

I’ve got those port numbers from this install page: https://marketplace.digitalocean.com/apps/docker

I have setup a firewall in my control panel: HTTP TCP 80 HTTPS TCP 443

but I’m still getting a 404 - nginx/1.10.3 (Ubuntu) page.

Any help would be appreciated. thanks.