- Pick a machine as the server which will host the repository.
- On the server machine, install subversion
- On the server machine, use svnadmin to create a new repository
- On the server machine, use svnserve.
- One each client machine, install subversion or tortoisesvn.
- Each client can check out the files from the repository created at step 3
This hasn't even gone into creating the trunk/branches/tags directory, which you should do. But that is pretty well documented.
At a high-level, svn://serverName/repositoryName/trunk should contain the VS project. All the developers check it out. Develop their changes. Commit them. Update to get everyone else's changes.
From a network-point of view, as long as the machines can see each other, that's all you need to do. If the machines are all on the same intranet, using svnserve will be ample. It can get more complicated by setting up http access into the repository, but you haven't said whether the developer's need http access. So assuming svnserve is sufficient.
Hope this helps.