Adding OAuth support to an existing n8n Docker image is not possible (OK is theoretically possible but would take incredible much work and would be a horrible mess). So what you would have to do is to build an own docker image.
How to do that @Talha_Khan described here (I never tested it):
If you have the “oauth-support” branch of n8n checked out you should be able to build an image like that which has then the current wip state.