If you're talking about the candy hearts for the week of love, you can sell them by going into your inventory, clicking them, clicking them over to "Sell Area", and then clicking "Sell Item(s)." However, I would recommend selling them to other players instead. You can do this by clicking the candy heart, clicking "Broker Item," then putting the selling price into the "Price per unit" box. They can catch a pretty good price.

See them on the broker. That'll give you a nice bit of gold as well. Just click on the heart, click on the broker button underneath the invent boxes, and type in how much you want to sell for then click the broker button in the popup window. Then later on you can go to he broker tab and collect the gold in your till if the heart sold (`}|` it should if it's not too high a price). Averahe is around 30-50k