Hi Alex! Thank you for your reply.
I have been doing Selenium test automation for some years now and I think that I'm quite familiar with XPath (and CSS). However, the thing is that for me, the XPaths in Appium look very different from the XPaths in Selenium. For example, in Appium, I see something like this.
By.XPath("//android.widget.RadioButton[@text='Use Testdroid Cloud']")
For Selenium, I can use for example Firebug in Firefox to extract the XPath of an element. I don't know yet, how to do the same for Appium.