FedEx Address Validation module setup help
Unless you desperately need those vars to be administered through the UI (in which case a small custom module would be the way to go), you can just add the variables through settings.php, using the following format:

$conf['fedex_address_validation_environment'] = 'test';
$conf['fedex_address_validation_live_key'] = 'foo';
$conf['fedex_address_validation_live_password'] = 'bar';
// etc...