You can exclude certain products from being eligible to earn commissions.
Step 1: Navigate to Affiliates -> Settings -> scroll to bottom of page:
Step 2: Click on Add SKU - the system will ask you to enter the product name and SKU.
For clarification though, this is the productID value. Different e-commerce platforms will have different terms for this value:
Shopify = ProductID
BigCommerce = ProductID
WooCommerce = ProductID / PostID
Magento = SKU
Maropost = SKU
Custom API = (depends on your platform).
If you wish to add products in bulk, click on the Bulk Import SKU - upload your CSV file -> save changes.