You’ll need to do an automated build of your Docker image. Basically, you’ll add the Dockerfile (and any related context) to a repo (GitHub, BitBucket, or your own), and Docker will build the image anytime it gets a webhook.
From the docs:
Automated Builds have several advantages:
Users of your Automated Build can trust that the resulting image was
built exactly as specified.The Dockerfile will be available to anyone with access to your
repository on the Docker Hub registry.Because the process is automated, Automated Builds help to make sure
that your repository is always up to date.