You just use aged accounts to engage and make it look like they're promoting a certain business through either new posts or comments or combination. And you can use tools or just Google to see which Reddit threads are already ranking for a certain keywords and then you would go to those pages and leave comments recommending your business etc

here's a more well-publicized and AI-ified example of how that's done: https://www.404media.co/ai-is-poisoning-reddit-to-promote-pr...