The following steps should be followed to open a GIT repository within Simplicity Studio V4:
1. Install Simplicity Studio V4 here - http://www.silabs.com/products/development-tools/software/simplicity-studio
2. Type CTRL-3 and in the search box start typing "Install New Software" and select the command when it is available.
3. In the "Work with:" window enter this url (it is the version compatible with Simplicity Studio): 'http://download.eclipse.org/egit/updates-4.11/' and click the [Add...] link. In the popup give it a name like 'egit' and then click [OK].
4. Only select the 'Git integration for Eclipse' checkbox in the available updates and then continue through to install the software.
Additional updates to some Simplicity Studio packages might be presented as well and if there are any it is okay to install those updates as well.
After the installation, Simplicity Studio needs to be restarted and then a "Git" perspective should be available within Simplicity Studio.
Information about Cloning a Git Repository can be found in this KB article.