In Excel 2011 for Mac OS X, after installing ChangeUnits you must select Add-Ins using the Tools menu.

In the Add-Ins menu that appears, select the ChangeUnits Add-In. Click OK and ChangeUnits is ready to use.

Science and Engineering Calculators
In Excel 2011 for Mac OS X, after installing ChangeUnits you must select Add-Ins using the Tools menu.
In the Add-Ins menu that appears, select the ChangeUnits Add-In. Click OK and ChangeUnits is ready to use.