Mac OSX LION and Snow Leopard comes with SVN Server by default. An easy tutorial can be found here
Basically you will be using command line (shell) environment. No GUI tool is available.
To create a repository issue this command
svnadmin create MyFirstRepository
This will create a repository with the above name in the current folder.
The next step is to import a directory. Use this command
svn import destination-folder file:///path-to-repository -m "Initial Import"
The third step would be to checkout what you just checked in.
svn checkout file:///path-to-repository destination-folder