Adding custom fields to a checkout form
Creating a custom field on your purchase receipt for the purposes of getting more information from your customer - i.e. their preferred T-shirt color, their shipping address, or their A/S/L - is easy!
First go to your product's CHECKOUT TAB and scroll down the page to Payment form.
Underneath the Payment Form box, click Add custom field
Type over "Enter Placeholder" the message you want your customers to answer, and click the box to require that box to be filled out before purchasing.
If you leave a field as optional, customers will see that on their payment forms:
If you simply want to require your customers to enter shipping information, you can tick the box Require Shipping Information.
Click Save changes to save changes. To delete a custom field, simply click the red X and save changes.