Hi there @ChefEquipment, 

Welcome to the Community! Happy you’re here! 

In order to do this, I would first  create a segment that will dynamically pull all users who fit into the condition : What Someone Has Done > Purchased X Product or X category > At Lease Once > Over all time. Then I would send a specific campaign to this select segment letting them know of the sale! 

Finally, I’d check out our awesome Academy courses to build on your Klaviyo knowledge such as :

• Getting Started with Klaviyo'
• Product Certification

Thanks for participating in the Community! 

-Taylor