Selling customized products on Shopify can be a great way to offer unique, one-of-a-kind items to your customers. Here are some steps to help you set up and sell customized products on your Shopify store:

1. Choose a product: Decide which products you want to offer customization options for, such as clothing, jewelry, or home decor.
2. Create custom options: Use the Shopify customization app to create custom options for your products, such as different colors, sizes, or personalization fields.
3. Add custom options to your products: Once you have created your custom options, add them to the relevant products in your Shopify store.
4. Set up pricing: Decide on a pricing structure for your customized products. You can charge a flat fee for customization or offer different pricing based on the complexity of the customization.
5. Create a customization page: Create a page on your website where customers can submit their custom requests, such as custom messages or images.
6. Promote your customized products: Make sure to promote your customized products prominently on your website and social media channels.
7. Fulfill orders: Once you receive an order for a customized product, make sure to communicate with the customer to ensure you have all the necessary information to fulfill the order correctly.
8. Keep track of orders and inventory: Keep track of all customized product orders and inventory to ensure you are able to fulfill orders in a timely manner.

By following these steps, you can start selling customized products on your Shopify store and offer unique and personalized items to your customers.

It’s also worth to mention that there are some Shopify apps that can help you with this process such as Custom Fields, Custom Product Builder and Product Personalizer. These apps can help you with creating, customizing and selling your products with ease, and they also have features like inventory management, order tracking, and customer communication.