Please know Affiliate System is Opencart's default Affiliate system where your Affiliate partner can signup for Affiliate account from the link given at the bottom footer of the website.

And after signup Affiliate partner will get his unique referral URL. By that referral url if any customer purchase product any product then that Affiliate partner will get the commission what you have saved in the admin panel => System => Setting => Edit Store => Option Tab and here find Affiliate section.

You can check affiliate partner details from Admin Panel => Marketing => Affiliate.