Hi Van!
Click here mate:
http://www.ozcardtrader.com.au/community/forums/submit-sale-trade-agreements.14/
Then post a new thread and give it a brief heading which has both members names in it (eg: "vansan & Matty76"). Mark the thread title as "In progress" from the dropdown box on the left.
In the thread itself you provide a brief explanation of the deal:
For example
"vansan gets Marc Murphy captain wildcard
Matty76 gets $$ paypal
Agreed?"
Then I would reply "agreed" below your post.
This of course is assuming the finer details have already been sorted out in a sale thread or through private messages. Basically the Trade agreement is a summary of what has been agreed.
I usually send a PM with a link to the thread I created so it's easy for the other person to find.
When the cards/funds etc are received and feedback given etc, edit the thread title from "In Progress" to "Completed", as that closes it off.
Hope this helps mate