If you have items to exchange with others, you trade with them: i. Click on the "Trade" button in the interface. ii. Click on the target player. iii. If the target agrees to trade, then your inventory will open and the trade window will also open.

Confirm: Type the amount of money and/or CP in the boxes, then click on "Confirm" to trade. Be aware that once you confirm the amount, you are unable to change it. The only way to change the amount is to cancel the current trade and start again.

Okay: Drag your items to the trading window, check if the money is right, then click on "Okay". If the other party clicks on "Okay" too, then the trade is completed.