First of all, you must be a member of Builders Club to be able to trade items with other users. To ensure that you are able to trade with other ROBLOX users, you need to make sure it is enabled in the account settings of your ROBLOX account.
Underneath your personal blurb, you should find the Trade Accessibility drop-down menu. It is up to you as to what setting you want, but please note that it affects who you can set up trades with, as well as who can set up trades with you. If set to "No One", the trade system on your account is switched off - you cannot create or accept trades.
You can only trade with BC members who have their Trade Accessibility set up so that you fall within their category and who fall within your own Trade Accessibility category. You can trade with any ROBLOX user who falls into both of those.
On the profile of the ROBLOX user that you want to trade with, next to Send Message, on the More drop-down menu, Trade Items should be present. If not, then check your Trade Accessibility setting. Clicking on Trade Items will then open this window in your browser:
In the trade window, all of your Limited items, and all of the other user's Limited items are displayed. They can be added into the trade by simply clicking on them, or can be removed again by hovering over the item in the current offer window, then by clicking the remove button below the item information:
While adding and removing items to and from the trade, you can keep on top of the current value of both your offer and what you are requesting from the other user:
Once you are happy with the trade request that you have got set up, you can send the request to the other ROBLOX user by clicking the massive, green Send Request button below the current offer.
A new feature that has been added to the Trade System is the ability to add Robux into the trade. This is very useful for trades that are worth more than a ROBLOX user has in Limited items. There is however the limiting factor where you must trade at least one item with any Robux you wish to trade. Also, a bit like the marketplace fee, 30% is taken from the Robux that you are trading.
That's it! You have now sent your trade to the other player, and it is now just a waiting game. ROBLOX will send you a personal message when the trade is either accepted or declined, or if it has expired.