In team fortress 2 how do you make yourself invisible with the magic mouse

You have to make sure you have right-click enabled, by going to (Apple Icon)>System Preferences>Mouse>Point and Click, and you should see a Secondary Click option. Make sure that is checked off, and if you want it to work like a standard 2-button mouse, choose "Click on Right Side" from the drop down menu, or you can choose "Click on Left Side" if you so desire. Then, when you are playing as Spy in TF2, simply click on the side of the mouse you have it set to, and you should cloak.