Now that you're trade request has been accepted, it's time to begin trading! (See Trading Basics if you're unsure on how to enter a trade.)
When a trade window appears, the screen behind it will darken. You can still see what's going on in the room behind you, but you can't use your toolbar to perform any actions other than trading. The trade window will have tabs at the top, labeled as Furniture, Clothing, Pins, and FX. By clicking on each of these tabs, you can see all of the items you have in your inventory that are available to trade. Once you've found the item you wish to add to the trade, double click it. The item will then drop down from your inventory into a box below labeled "Your Offer." To the right of "Your Offer" box is the other player's trading box. In this box, you can see what items that player is offering to trade.
If you decide to take an item out of the "Your Offer" box, double click the item again and it will disappear from the offer box and remain in your inventory.
If you want a closer look on an item in the trade, click on it and a close-up picture of the item will appear on the bottom right corner of the trade window.
If you wish to chat with the player you're currently trading with, click on the white horizontal bar near the bottom of the trade window. Type whatever you'd like to say to the other player and then hit the "Enter" or "Return" button on your keyboard to send the message. Your message will then appear above the white typing bar in another box below the "Your Offer" box.
If you decide that you really like the player you're trading with and want to hang out with them or trade them again, click the green "Ask to be Friend" button at the bottom left of the trade window. Clicking this button will send a request to the other player, asking them if they would like to be your friend.
If you've decided you've had enough of trading and want to leave the trade click either the red "End Trade" button to the right of the "Ask to be Friend" button or click the "X" button at the top right corner of the trade window. If the other player leaves the trade, the trade window will disappear for you and a dialog box will appear telling you that the player has "Ended the trade."
If, however, you don't want to close the trade, but want to accept the other player's offer, there are several steps to follow. First, click the small white box below the "Your Offer" box. This small white box will be labeled "You Accept." After the other player also accepts your offer, another window will open. In this window there will be a box on the left and a box on the right. The left box shows the item(s) you've offered for trade and the right box shows the item(s) the other player has offered to trade. If you've decided that you don't want to make this trade click the red "Cancel" button below these boxes. If you've decided that you want to trade click the green "Confirm" button, also at the bottom. Once you've confirmed your offer, a message will appear below your offer box saying you've confirmed. Once the other player has also confirmed their offer, all trade windows will close. Your new item(s) will now be in your inventory!