iMac

The Magic Mouse only has one click which is the usual Left-click. To simulate the Right-click, hold down the Control key and them click the mouse. Alternatively, open Mouse preference pane, click Point & Click button. The second option is labeled, "Secondary click." You can check the box, then click on the tiny upside down caret and select the desired option.

Visit System Preferences : Mouse panel, and select Secondary click as shown below. Then left click with index finger, and right-click with adjacent finger. No need to control-click though it will still work. I am using an Apple Magic Mouse 2.