If your system is on 10.9 or newer, use these instructions - https://echo1612.freshdesk.com/support/solutions/articles/24000014201-mac-enable-accessibility
Mac Enable Accessibility (Legacy OSX Mountain Lion 10.8)
Open System Preferences > Accessibility
Check the box next to "Enable access for assistive devices"
Mac Enable Accessibility (Legacy OSX Lion 10.7)
Open System Preferences > Universal Access
Check the box next to "Enable access for assistive devices"
