If you have trouble emptying your trash on your Mac computer, you will need to launch the Terminal first, in order to begin troubleshooting the issue. The trash will often fail to accept items, if it believes that a program or object is in use. Move the application that you can't delete onto your desktop. Add a line of code to the terminal. Add the application to the code, by dragging it to the code. It will ask for your code. Enter your password. Press enter. You will need to use a Sudo code, and it must be entered correctly. Typos may cause permanent damage to your computer.