Go to the Finder - click anywhere on your Mac's desktop, and choose File > New Folder.
If a folder appears on your Desktop then continue reading. If not, stop reading.
Open Terminal - it is in your Utilities folder and looks like this
You can find Terminal by using the Finder's Go menu and choosing Utilities, then double-click the Terminal icon.
Copy (drag or triple-click to select the line) and Paste the following commands into the Terminal window, each one followed by the Return key:
mkdir ~/.Trash
If you get the message "File exists" you can ignore it.
Next Copy and Paste the following line, followed by the Return key:
sudo chown $UID ~/.Trash
This time Terminal will ask for your Admin password - the same one you use when you log in to your Mac. Type it and then press the Return key. What you type will not appear, not even with •••• characters.
Next Copy and Paste the following:
chmod u+rwx ~/.Trash
To summarize the above you will be doing this:
Last login: Wed Feb 12 03:21:53 on ttys000
Johns-iMac:~ john$ mkdir ~/.Trash
mkdir: /Users/john/.Trash: File exists
Johns-iMac:~ john$ sudo chown $UID ~/.Trash
Password: (type your password then press Return)
Johns-iMac:~ john$ chmod u+rwx ~/.Trash
Johns-iMac:~ john$
You will be typing the entries in red exactly as shown.
Quit Terminal.
Drag the empty folder you just created to the Trash, confirm that it appears in the Trash, and that you can empty the Trash.