How to select locator for checkboxes

Here i have to select the checkbox using selenium and i am not able to select it it have only one optin of classname that i am using but error is appearing error: org.openqa.selenium.NoSuchElementException: no such element: Unable to locate element: {"method":"class name","selector":"um-icon-android-checkbox-outline"}

code

@Test
public void validemail()
{
    WebElement email=driver.findElement(By.id("username-15"));
    email.clear();
    email.sendKeys("ceicateviewer");

    WebElement password=driver.findElement(By.id("user_password-15"));
    password.clear();
    password.sendKeys("1256Aa");

    WebElement showpassword=driver.findElement(By.className("um-icon-android-checkbox-outline"));
    showpassword.click();

    WebElement keepsignin=driver.findElement(By.className("um-icon-android-checkbox-outline"));
    keepsignin.click();


    /*WebElement login=driver.findElement(By.className("um-button"));
    login.click();*/
}