Find an agent plugin aka a harness for your IDE that doesn't require a subscription, unless of course you enjoy giving money away. Some agents are configured to work with particular providers, others are 'bring your own key', so again it depends on whether you like being locked in to someone else's ecosystem and paying acordingly. you can also get harnesses that are self-contained rather than being part of an IDE, but I assume you like your existing tools.
Take the API key you got from your AI service, plug it into the agent. Start building a toy project; the easiest is something that you have previously made yourself so you know something about the data structures involved, problems you're likely to run into and so on. Treat the agent like your assistant. I prefer asking it to draft a plan of what it's going to do which I then approve rather than just setting it free and then puzzling over the output, you may evolve a different approach.