How do you sell an item to a specific person? I want to help someone with their wish but i don't know how to get the item to the person.

Assuming the item is your inventory and ready to go, do the following:

Go to your inventory.
Select the item.
Click on the envelope with the green arrow at the bottom of your inventory.
Fill out the name of the player you're sending it to, as well as the amount of gold in the "COD" box if it's a sale.
Hit "Send item" when all information has been filled out.