Do I still need to click on my item in my "Your Items" and put it up for trade to be able use it at the Trading Post?

Previously you couldn’t add items to trades from your inventory, but now you can! You can also go to the Trading Post to create a lot, where you will see a list of all of the things in your inventory automatically that are not up for auction or being used in any other way. All you have to do is go the Trading Post and start trading!