Spencer Haws from Niche Pursuits points out that there are advantages to building a more targeted micro niche site. That way, you can cover a topic more in-depth and send lots of authority signals to Google that you should be ranking well for the terms. “If all you write about is tents, you will likely have more topical authority for that particular subject than if you were writing more broadly just about general ‘camping’ topics.”
Tell your email list about it. If you have an engaged email list, and I hope you do, it will almost always outperform a blog post. You may choose to (sparingly) write a dedicated email about something you love, or just link to it as it fits naturally within your story. Or, add a P.S. to the bottom of your email if you have a special sale or coupon code to share.

In most cases, it's up to you how to promote your partner's product. You can recommend the product to your existing audience via email, blog posts, or social media posts. Alternatively, you can attract new audiences on behalf of your partner, like build a dedicated website and bring SEO and PPC traffic to it, organize training courses, launch promotional sales, etc. But the idea always remains the same: affiliate marketers refer new clients to a partner's website and get paid for that.
Even if you’re super passionate about a niche, there’s no point in starting an affiliate blog if you can’t monetize it.