Click the bottom left lock to adjust the settings and set Accessibility on Terminal to checked. Search for Security and Privacy, enter the main administrator password and allow the Terminal app to have access to the mouse. When you try to start the clicker, a warning should appear about Accessiblity settings. More directions if you get stuck on opening the program. Right-click, Open, and Open anyways if an error appears about this.
Ignore any warnings about developer signing. The Auto Clicker for Intel Mac download is now available for older Intel Macs.
