deploy a docker image in general and with django

I struggle to grasp how to expose a docker image that exists in DO droplet or a registry.

Precisely, I’m looking at how to connect the doecker-compose image to the droplet/application.

I created a docker droplet, installed docker-compose on it (ubunto 20.04).

From docker-hub and/or github I then pushed the image to the droplet

Separately, I also push it to the registry.

on Doctl I then run docker-compose --build

and then: docker-compose up -d

I can observe that the image exists was build on the droplet, or pushed to the registry. But then, what happens next? How I can display the up image on my droplet or my application?

I wish to avoid cubernetics to tackle my problem, as it adds another layer of complexity.

Any input would be highly appreciated.