These instructions refer to macOS Big Sur (11).
However, the procedure is the same or similar in earlier versions ofmacOSand OS X.
Launch System Preferences by clicking theSystem Preferencesicon in theDockor by selecting theSystem Preferencesitem under theApplemenu.
In theSystem Preferenceswindow, select theMouseicon to open theMousepreference pane.
Go to thePoint & Clicktab.
Select theSecondary clickcheck box.
Choose either right or left.
CloseSystem Preferencesto save the change.
How to activate the Second Button on a Mighty Mouse
The Mighty Mouse preceded the Magic Mouse.
Launch System Preferences by clicking theSystem Preferencesicon in the Dock or by selectingSystem Preferencesunder theApplemenu.
Click theMousetosee a pictorial representation of your Mighty Mouse.
The default configuration has both the left button and the right button assigned toPrimary Click.
Use the drop-down menu associated with the button you want to change and selectSecondary Click.
Otherwise, follow these instructions:
Launch System Preferences by clicking itsDockicon or selecting theSystem Preferencesitem from theApplemenu.
In theSystem Preferenceswindow, click theMouseorKeyboard & Mouseicon to bring up the preference pane.
Click theMousetab, if needed.
Assign thePrimary Clickmouse button to either the left or right mouse button.
After you make your selection, the secondary click function is assigned to the remaining mouse button.
This action creates the equivalent of a secondary click.
