Well, we don't use VS 2012 yet and I've not tried this with VS 2012, but I'll give it a shot.

1) Get Sql Server Data Tools! Download and install the appropriate version for you, there's one for VS 2012.

http://msdn.microsoft.com/en-us/data/hh297027

2) Create a new database project (make sure it's the SQL Server Data Tools project though, and not the default Visual Studio database project)

3) Reverse-engineer your database into your project. I use the "Schema compare" feature to do that, but I don't think that's the only way.

4) Add your project to TFS

That's basically it. Once you have the project in Visual Studio and have added it to TFS, you're pretty-much good to go.

You'll need to do your own research on how to use SQL Server Data tools, there's a lot to it and I can't possibly explain it all, especially since I don't use all of its functionality. There's plenty out on the internet to show you how to do that, though. Here's a link to a Tech-ed presentation on it:

http://channel9.msdn.com/Events/TechEd/NorthAmerica/2011/DEV207

But google for SSDT or "SQL Server Data Tools" and you'll find lots of info.