Upload the plugin files to the /wp-content/plugins/Affiliates-Referrals-for-Woocommerce directory, or install the plugin through the WordPress plugins screen directly.
Activate the plugin through the 'Plugins' screen in WordPress
Then open the Dashboard->Referrals.
Select an affiliate from the dropdown an set the referral rate below and press save.Thats it.
You can edit the referral rate at any time by opening Dashboard->Referrals->Referral Edits