Upgraded TFS to 2013, wanted to use SP 2010 but broke it. Reattached WSS_Content but it still is broken

I upgraded our TFS2012 to 2013 (and SQL 2008R2 Enterprise to SQL 2012 Standard).

TFS2013 is supposed to be compatible with SP 2010.

To cut a long story short, I broke sharepoint. I started a new farm and attached the content database WSS_Content. All our sites were listed, but when I tried to visit them they didn't exist.

How do I restore WSS_Content correctly so that all our sites and documents can be seen?