What Etsy have managed to do is become the leading platform in their niche – nobody else comes close. They’ve gone from zero to publicly traded company in a very few short years.
You can simply sign up for the program and get your unique tracking link. Now, whenever you are writing about their product, you can simply use this special tracking affiliate link to recommend the company’s site. If your readers/traffic buys anything by clicking your affiliate link, you will get a commission.

Another way to promote your affiliate links is with useful resources that provide a lot of value; for example: Checklists: for example, if you had an SEO blog you could create something like a “SEO blog writing checklist” and promote any relevant tools that would help your readers improve their SEO resultsE-books: write short e-books (30-40k words) that allow you to cover a subject in-depth; like with how-to guides, you’ll be able to include relevant affiliate links throughout your e-book, by recommending quality products and services based on the tips and advice you’re offering Recommended products/services page
However, this is just one example in one niche. If you’re in other niches it’s worth looking at who is offering their own affiliate programs, or products/courses that might work with an affiliate model. Increasingly, selling leads to businesses is becoming a really solid model for affiliate marketers to begin pursuing.