The problem with affiliate marketing, like many other home business options, are the so-called gurus and get-rich-quick programs that suggest affiliate marketing can be done fast and with little effort. Odds are you've read claims of affiliate marketing programs that say you can make hundreds of thousands of dollars a month doing almost nothing ("Three clicks to rich!"). Or, they suggest you can set up your affiliate site, and then forget it, except to check your bank deposits.
If you have an e-book or online course that you'd like to promote, ClickBank makes that easy. Once you sign up as a vendor you can list your product with them and set the commission percentage you are willing to pay to anyone who chooses to market and promote your product for you. Once your product is listed, other ClickBank users will start promoting it on their own websites. This will drive traffic to the sales page on your website and hopefully result in sales.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.