IntelliJ - Convert a Java project/module into a Maven project/module
Right-click on the module, select "Add framework support...", and check the "Maven" technology.
(This also creates a pom.xml for you to modify.)
If you mean adding source repository elements, I think you need to do that manually–not sure.
Pre-IntelliJ 13 this won't convert the project to the Maven Standard Directory Layout, 13+ it will.
A visual for those that benefit from it.
After right-clicking the project name ("test" in this example), select "Add framework support" and check the "Maven" option.
- Open 'Maven projects' (tab on the right side).
- Use 'Add Maven Projects'
- Find your pom.xml