IntelliJ IDEA 13.1.0 Web Help

From the Welcome screen (if no project is currently open): Import Project
File | Import Project
File | Import Module
From the Project Structure dialog: Modules | add | Import Module

Use this wizard to import existing sources into IntelliJ IDEA and, as a result, to create a new project (Import Project) or to add a module (or a number of modules) to an existing project (Import Module).