Hello Urmila, to parallelly execute automation tests using Selenium Grid, you can use following code snippet:
public class Parallel_Execution_Test
{
    WebDriver driver;
    String nodeURL;
    @Parameters({"Port"})
    @BeforeMethod()
    public void setUp(String Port) throws MalformedURLException
    {         
        if(Port.equalsIgnoreCase("4546"))
        {
            nodeURL = "http://10.0.0.22:4546/wd/hub";
            System.out.println("Chrome Browser Initiated");
            DesiredCapabilities capabilities = DesiredCapabilities.chrome();          
            capabilities.setBrowserName("chrome");
            capabilities.setPlatform(Platform.WINDOWS);
            driver = new RemoteWebDriver(new URL(nodeURL),capabilities);
            driver.get("https://www.google.com/");
            driver.manage().window().maximize();
            driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
        }
        else if(Port.equalsIgnoreCase("5566"))
            {
                nodeURL = "http://10.0.0.22:5566/wd/hub";
                System.out.println("Firefox Browser Initiated");
                DesiredCapabilities capabilities1 = DesiredCapabilities.firefox();
                capabilities1.setBrowserName("firefox");
                capabilities1.setPlatform(Platform.WINDOWS);
                driver = new RemoteWebDriver(new URL(nodeURL),capabilities1);  
                driver.get("https://www.google.com/");
                driver.manage().window().maximize();
                driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
            }
        else if(Port.equalsIgnoreCase("4547"))
        {
            nodeURL = "http://10.0.0.22:4547/wd/hub";
            System.out.println("Internet Browser Initiated");
            DesiredCapabilities capabilities2 = DesiredCapabilities.internetExplorer();
            capabilities2.setBrowserName("internet explorer");
            capabilities2.setCapability(InternetExplorerDriver.INTRODUCE_FLAKINESS_BY_IGNORING_SECURITY_DOMAINS, true);
            capabilities2.setCapability(InternetExplorerDriver.IGNORE_ZOOM_SETTING, true);
            capabilities2.setCapability(CapabilityType.ACCEPT_SSL_CERTS, true);
            capabilities2.setCapability("ignoreProtectedModeSettings", true);
            capabilities2.setCapability("nativeEvents", false);
            capabilities2.setCapability(InternetExplorerDriver.INITIAL_BROWSER_URL, "");
            capabilities2.setCapability(InternetExplorerDriver.LOG_LEVEL, "DEBUG");
           
            capabilities2.setPlatform(Platform.WINDOWS);
            driver = new RemoteWebDriver(new URL(nodeURL),capabilities2);
            driver.get("https://www.google.com/");
            driver.manage().window().maximize();  
            driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
        }
    }
    @Test
    public void googlePage() throws InterruptedException
    {
        try
        {
        driver.findElement(By.xpath("//*[id=search")).click();
        Thread.sleep(2000);
        driver.findElement(By.cssSelector("#chapternav > div > ul > li.chapternav-item.chapternav-item-ipad-air > a > figure")).click();
        Thread.sleep(2000);
        driver.findElement(By.linkText("Google Search")).click();
        Thread.sleep(2000);
        }
        catch(Exception e)
        {
            System.out.println(e.getMessage());
        }
    }
    @AfterMethod()
    public void tearDown()
    {
            driver.quit();
            System.out.println("Browser Closed");
    }
}
Now create the testing.xml file to pass parameters:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite thread-count="3" name="MultipleBrowser" parallel="tests">
  <test name="Chrome Test">
  <parameter name="Port" value="4546"/>
    <classes>
      <class name="DemoAutomation.Selenium_MultiBrowser_Test"/>
    </classes>
  </test>
 
  <test name="Firefox Test">
  <parameter name="Port" value="5566"/>
    <classes>
      <class name="DemoAutomation.Selenium_MultiBrowser_Test"/>   
    </classes>
  </test>
 
  <test name="Internet Explorer Test">
  <parameter name="Port" value="4547"/>
    <classes>
      <class name="DemoAutomation.Selenium_MultiBrowser_Test"/>
    </classes>
  </test>
 
</suite>