IntelliJ IDEA supports version control integration at two levels:
At the IDE level, VCS integration is provided through a set of bundled plugins enabled by default.
At the project level, VCS integration is enabled by associating project folders with one or several version control systems.
Perform below steps:
To add an existing project under Git −
Navigate to VCS → Import into Version Control → Create Git repository.
Select a project by browsing the directory.
Click on the OK button.