Hey usha, to launch PhantomJS driver using Desired Capabilities in Selenium, you can use this code snippet:
public static void main(String[] args) {
            DesiredCapabilities capabilities = new DesiredCapabilities();
            capabilities.setJavascriptEnabled(true);
            capabilities.setCapability(PhantomJSDriverService.PHANTOMJS_EXECUTABLE_PATH_PROPERTY, "C://phantomjs.exe");
            capabilities.setCapability("takesScreenshot", true);
            WebDriver driver = new PhantomJSDriver(capabilities);
            driver.get("https://www.google.com");
            driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);
            String title = driver.getTitle();
            System.out.println(title);
    }