Step 2: Click on the confirm button.

Step 3: Locate the material you would like to confirm exchange with.

Step 4: That's it! Once you confirm an exchange your material will disappear from the website as long as the max quantity has been reached.

If you want to remove your item before you confirm the exchange with someone you can access your "My Profile" page, and click on a link "Edit/View Listings", this will allow you to remove the listing from the website as well.