Make sure you've got the basic System Requirements setup
Run the selendroid-standalone server:
java -jar selendroid-standalone-0.17.0-with-dependencies.jar
Start your driver using Selenium's "Android" Desired Capability:
WebDriver driver = new RemoteWebDriver(DesiredCapabilities.android());
driver.get("http://google.com");
A full sample about how to test the mobile web in Java you find here.
driver = Selenium::WebDriver.for :remote, :desired_capabilities => :android
driver.get "http://google.com"
driver = webdriver.Remote(desired_capabilities=webdriver.DesiredCapabilities.ANDROID)
driver.get("http://google.com")