In order to install Claris CAD fonts, you must use Font/DA Mover 3.8 or later. Any version below 3.8 will not recognize the Claris CAD fonts, because they are the newer NFont type fonts.
To install the font under System 7, simply drop the font onto the System folder and click OK when it asks if you want to put it in the System file. You could also drag it directly onto the System file.