How do I empty my trash from my MAC computer?

FWIW, you can also right or control click on the Trash icon and choose "Empty Trash', or while in the Finder, choose "Empty Trash" from the Finder menu or press "command shift delete" to avoid opening the Trash window.

Click on the Trash icon in the dock and then click the "Empty" button near the top right of the Trash window in Finder.