Use any of below XPath
//input[@type='password']
OR
//input[@name='password']
OR
//input[contains(@aria-label,'Enter your password')]
OR
//input[contains(@autocomplete,'current-password')]
The complete code will like below :-
driver.manage().timeouts().implicitlyWait(60, TimeUnit.SECONDS);
driver.findElement(By.name("identifier")).sendKeys("xxx@gmail.com");
driver.findElement(By.xpath("//span[contains(.,'Next')]")).click();
driver.findElement(By.name("password")).sendKeys("123456");
WebDriverWait wait = new WebDriverWait(driver, 10);
WebElement element = wait.until(ExpectedConditions.presenceOfElementLocated(By.xpath("//span[contains(.,'Next')]")));
element.click();