No worries! you go to your inventory by clicking the bell bag icon on the home bar, find the little cherry (or whatever item you are trading) and click gift! Then type in the username of the person you are sending it to, and then leave a message!
In this case, find the perfect cherry, click gift, type Mr_Keroppi and then leave a cherry emoji in the message box! I’ll send you the orange now!
If you want to see the orange under your profile, go to the settings in your inventory and set it as active and unhidden!