When you first activate an Android phone, there is a short tutorial that walks you through the home screen, adding icons/widgets to the home screen, navigating the home screen, etc. On stock android, there is also a helpful widget on the homescreen.
For many phones, there is a small booklet (often called the manual) in the box when you purchase the device. These booklets can also be found online, for example some popular Android 4.0 devices: Galaxy Nexus user guide, or Galaxy S3, or HTC Incredible. You can find manuals for your device by browsing the manufacturer's website or googling for "(device name) manual" or "(device name) user guide".
Manufacturer websites also typically have a Knowledge Base, Support Center, etc. For instance, HTC Support Center for Desire X or Samsung Support for Galaxy Note.
Finally, there are also Android StackExchange and other Android-related forums which contain lots of helpful people willing to answer your questions. If you're still unclear on anything specific, ask away!