How To Collect Additional Information with My Products (Custom Fields)
Custom Fields are used to collect additional information needed for orders, specifically for off-line Products. To setup Custom Fields for a given Product, go to Settings > Products, click edit for the product in question, and scroll down to the Custom Field Section.
Click add to add a plan or click the remove button to remove a plan (it will only be removed after you save).
Fields added here will be collected during the checkout process. For more info on the different Custom Fields Settings, click here.