All you need to do to integrate the eLearnCommerce Sales Engine with AffiliateWP is to go to Affiliates -> Settings -> Integrations and set a Checkmark on eLearnCommerce Sales Engine.
The integration with AffiliateWP is a native one, this means you do not need to install any further addons to start tracking your sales with AffiliateWP.
Just install eLearnCommerce + the eLearnCommerce Sales Engine + AffiliateWP and you're good to go!