As indicated by the following screenshot, you can access Unity's documentation and scripting manual using the Help menu selection:
Additional functionality available via the Help menu is as follows:
Help Content | Description |
Unity Services | This menu option takes you to a Unity page that serves as a gateway to information about integrated Unity services. |
Unity Forum | This menu option takes you to the Unity forums site, which features several different Unity forums and includes a search feature. |
Unity Answers | This menu option takes you to the Unity Answers web page. Here you can ask new questions about Unity development and search ... |