To work with a Subversion (SVN) version control in Xamarin Studio (Mac), you can use the following steps to connect your project to an svn repository on your local machine:
1. Create an SVN repository form the command line with:
svnadmin create /path/to/repository
2. Open or start a Xamarin Studio Project.
3. Right click on the solution and select Version Control -> Publish.
The project will stay in the same place, so if you want it within the repository directory, make sure your project/solution directory is in the svn repository you created in step 1.
4. Select Subversion for the top drop down.
5. Select "file" for Protocol.
6. In the Url field, enter the absolute path to the repository root folder, the same you created in step 1, /path/to/repository.
7. Click OK.
8. You should now see all of the version control commands available in the version control menu.
 Screencast: http://screencast.com/t/sKwkwCd4Q
Just change the protocol (step 5) and Url (step 6) to publish to a remote repository.
You will need the Xcode command line tools installed, which should install automatically. You can check if you have SVN installed in Terminal with the command:
(Note: There is currently a bug that may prevent using subversion in the alpha and beta channels at the time of this writing (Oct. 17, 2014); but it's fixed in the Xamarin Studio 5.5 stable release: https://bugzilla.xamarin.com/show_bug.cgi?id=20770)