Voucherify allows for launching product-specific campaigns. E.g. you can make a coupon valid only if a customer purchases a given product. To start creating your product oriented deals, you should import product details to Voucherify. You can achieve it in two ways, with the Dashboard and through the API.
To learn about product management in the UI visit http://support.voucherify.io/article/52-product-manager
There 2 endpoints responsible for adding products and their variants, here's the part of API reference you should be interested in.
Play around with Products and SKUs API - catalog TC6 - Campaign with Validation Rules. Go to Postman examples