"Use" Command with CI?

I've installed PhantomJS and PHP-PhantomJS per the PHP-PhantomJS docs.

Per the PHP-PhantomJS docs, I have the following lines at the top of a controller file:

Code:

   use JonnyW\PhantomJs\Client;
   $client = Client::getInstance();

When executing `$client = Client::getInstance();`, I get the error:

'JonnyW\PhantomJs\Client' not found

The installer has placed `JonnyW\PhantomJs\Client` here:

/Applications/myWebApp/vendor/jonnyw/php-phantomjs/src/JonnyW/PhantomJs/Client.php

The controller that contains the "use" command is located here:

Code:

/Applications/myWebApp/application/controllers/myController.php

How can I modify the "use" command so as to locate the required "JonnyW\PhantomJs\Client" file?

Thanks in advance to all for any info.