How do I sell or launch my product idea?

There’s no right answer, especially since you havent told us what the product is.

Hope this will help:

1. Create an instagram page and make 9-10 posts with really good photos of your product.
2. Create a store on shopify. You can use a basic theme or get a third party theme if you do not have the budget to pay over $300 for shopify premium theme.
3. Make sure the site is designed well and clean. Should include all legal pages like privacy, terms, return policy, refund policy, shipping details and so on.
4. Integrate with a payment partner to handle payments on shopify.
5. Create facebook page, sign up for meta business account, connect fb page and insta account and add it to ads manager
6. Create a facebook pixel and connect it to shopify to track data from your users/customers. Enable share data and use the maximum option.
7. Run sales campaign right away. Try running a combination of both images and videos and go broad on the targeting. Your ad copy should be your targeting. Your target audience, problem and solution should be in your ad copy.
8. Run ads for 3 days at a budget equal to your product price. i.e, if your product price is $50, you minimum ad budget per day should be $50. Run for 3 days and see if there are any sales.
9. If you get sales. Awesome. Learn about scaling ads and making the site looking better.
10. If no sales and if you have budget to burn, try different ad angles, monitor your metrics and see if your audience responds.

This is very complex to explain here. But this is the basic idea. You will have to put in serious effort and learn how to do this correctly and execute.