Hi there!
For this you could use the free system with its built-in User Registration integration, or one of the free from integrations that support referred user registrations:
Alternatively, you could have it track actual referred orders if you use the Affiliates WooCommerce Light integration. This could make more sense and would be easier to handle if you have lots of different products.
A note on your topic’s title – as you mention pre-sale, please note that the forum rules here prohibit posting about commercial products. If you consider or are already using one of our premium versions, please use the support forums on our site instead.
Anyhow, if your question is only related to the free version and you have more questions, please feel free to follow up here.