Android's website offers tutorials on the Android Operating System for phones. Additionally, Google's support website offers a step-by-step guide to using the Android Operating System.
From the Android home page, click Devices and select Phones. Click any section under Get More Out of Your Android Phone for specific instructions on using features of Lollipop, Android's latest operating system as of 2015.
From the Google Help page, click the arrow icon to expand the selection. Under the Consumer section, click Android OS. To access a generic step-by-step Android guide, click Step-by-Step Guide to Switching to Android. This tutorial applies to cellphones only.
For specific Google products, choose the product for which an Android Operating System guide is needed. Google also supplies device manuals for the Nexus S, Xoom and ADT-1 Developer Kit.