WP Shop Cart allows you to capture customer input at the time of purchase. For example, if you are engraving items you could create fields that say, “Enter name to engrave” so your customer can enter a name that needs to be engraved.
To use this option, simply select “Collect Customer’s Instruction?” to “Yes” and add an instruction in “Instructions for customers” box under “Additional Product Details” when saving or configuring the product.
So before checkout, customers receive your instructions and enter their input.
Note: You can also instruct your customers to enter custom instructions at the checkout on PayPal’s check out page. PayPal lets your customers add a note (up to 300 characters) when checking out.