Just like a real-world funnel, a sales funnel acts similarly. It funnels down visitors through several stages before they become buyers. The way Henry explains it, if you're not creating an emotional attachment during each stage of that funnel, then you're largely wasting your time. It has to start from the very beginning, and it has to carry out all the way to beyond the purchase.
If you have built up an email list, you could also promote your affiliate offers via email promotions. Just make sure you build up a relationship with your audience first instead of going for the hard sell straightaway. The emails you send out must contain your affiliate links to products so when your audience click through. the sale is attributed to you.