Do you mean the trashcan on your desktop or the one in your e-mail account?
The desktop one needs to be emptied right click it and choose empty bin.
Your e-mail one may be different but they usually empty every week or so but you can usually delete the contents of this by highlighting the files and choosing delete from the menu or on the keyboard.
Without knowing exactly which type of e-mail account you have I can only talk in general terms.