Hi,
1.
This is a drag and drop interface, so :
- The 2 first rows are the Item that you'll have to drag and drop through your different steps
- The 2 box through the row 3 are 2 checkout steps, so you'll have to drag and drop your checkout items through these box regarding the step where you want your item to be.
2.
The Fields Item will be used to display custom fields from the "Order" tables, and sure the buyer will be able to add a message for the seller, which will be attached to your order.
3.
You'll have to read it left to right
.