How do I get celebrities to promote my product?

There are a few ways to get a celebrity to promote your product, but I'll bring up one way since you brought up Fashion Nova. Fashion Nova pays celebrities to post their clothing, and also pays celebrities to be brand ambassadors. They will even pay IG pages to post photos of the celebrities that are wearing their brand.

You can set-up these types of deals by first putting together a budget of how much you are willing to spend. Then you should build a list of celebrities that would likely fit within the budget. Once you have that ready, you can begin reaching out to the agents or managers of the celebrities and negotiate a deal to where you send them clothes, and you can pay them to post about it or use their pictures of them wearing your clothes to promote your brand in other areas.