The 1'st step is to find out: which products affiliates are making money from at the moment. Fundamentally, you need to follow the money.
The next step is to build an affiliate web page where you can promote these products.
Finally, you need to send as much traffic as you can to your "affiliate page", site or blog.
A Launch Date
When you Google search for "affiliate marketing launches", you will find bunches of sites where you can learn about upcoming launches. This method is sometimes known as "launch jacking" because you are benefitting from the buzz and momentum surrounding a current or future launch. Sites like Munchie have started easily divided into "big launches" and "all launches". The "big launches" are from reputable sellers and are probably the best place to start to gain affiliate sales.
Build, Host, Promote
When creating your affiliate page you could use a free website builder like Wix or Weebly or a free blogging platform like Blogger. Another option and probably the preferred route is to register a domain name and build a simple WordPress site so that you can either review one product or compare many products.
Traffic can be paid or organic, depending on your time and budget. If you are going down the paid route, Facebook ads are a good option as you can target your preferred customer type. Be sure to split test a couple of ads and start off with a small budget. The organic traffic you can help along with articles, blog posts, review videos, and social media posts. Finally, if you have built up an email list of interested prospects or customers, this should be one of your best traffic sources.