How are EDI code conversions assigned to a trading partner?

Hello, I've read through the ECE implementation manual and still cannot understand how a code conversion is assigned to a trading partner.  Also, in the Code Conversion Values, what values do I enter in the Key 1, Key 2...etc fields?

Let's say that trading partner (ABC) uses the code F340 (Pick/Up) for special charges.  In Order Management, I have a freight carrier called PICK UP.  

Let's also say that trading partner (DEF) uses the code F360 (Pickup - Out of Area)

questions:

1.  How would I set this up so that in the INO, TP ABC's file has F340?

2. Can someone look through the attached screen shot to explain these fields?