How to create an order form?

I am needing to add a t-shirt order form to a conference registration form. EXAMPLE: Group Registration = 10 people = t-shirt sizes & quantity??? 

PLEASE HELPPPPPP

If I understood correctly, you want to create an order form. 

You can create sub-products and enable quantity. Please check the following guides:

Setting Up Your First Order Form

Create Sub-Products Based on a Product Option

How to Add Options to Payment Forms