Blender on iMac

I'm a complete beginner, trying to learn to use Blender 2.90.1 on an iMac (running Catalina 10.15.7). I've bought a hard copy manual but I'm stuck because, even though the software I downloaded is specifically for Apple, Blender seems to assume I have a PC mouse with three buttons (see bottom left of attached screenshot) and my mouse only has one button. Can someone help me with this?
 

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One way to right click on a Mac is to press the Ctrl (or Control) key when you tap the mouse button, or the trackpad. Don't confuse the Ctrl key with the Alt (or Option) key. The Ctrl key on a Mac is not the one next to the space bar, it's at the far end of the keyboard, on either the right or left side.
 
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