Initiating a Trade
You can trade with other players by either typing /trade playername in the chat, or by hitting Tab, finding the person under Nearby Allies, and selecting Trade. If you initiate a trade, you need to hold still and wait for the other person to come to you. If you move, you will cancel the trade. If someone else initiates a trade with you, you can trade with them regardless of distance by typing /trade in response.
The Trade Process
Under "Your Offer", you can select the item(s) you want to trade by clicking on the + button. Underneath that, there is a section where you can input the amount of gold you want to trade to the other player.
Under "Other Offer", this tab will show you the items and gold the trader wishes to give to you.
Under "Transaction Fee", it will display the fee and you can change how the fee should be paid. The first button switches the currency to be paid as the fee (Gold / Iron). The second button changes who pays the fee or if the fee is split between players.
Under "Complete the trade", you can accept the trade by clicking on the first button.