Shortcode from Checkout Page in MarketPress


In the confirmation message using Manual Payment gateway, I want to use this shortcode: CUSTOMERNAME

I do not need Shipping info.

But in the Checkout Page,
there are only Two fields:
- Email*
- Special Instruction

To use the shortcodes in email followup, I need four fields:
- First Name*
- Email*
- Phone
- Special Instruction

How can I edit the Checkout Information page?