Problems getting started in SSRS

Clearly the hard part (so far) is just getting the right stuff installed and running.

I made perhaps the naïve assumption that I could design and debug/run reports locally before publishing to our server. I am running Windows 7 and have (I think) everything installed. I have SSDT-BI VS 2012 installed, I installed Reporting & Integration Services form the SQL Server 2012 we have. I have been in the configuration manager and applied the defaults. I can see SSRS & SSIS are running in services (even restarted them).

Going to the ReportServer URL fails with a very generic and unhelpful message: rsServerConfigurationError. I looked into the SSRS log files for more information: No DSN present in configuration file

Not sure what DSN I need to make, if in fact I need to...who knows.

Now, I don't have the full SQL Server installed on my machine, just express, which was already there.

I just really don't know where to look next for a solution. As it is I have VS 2005, 2008, 2010 & 2013 installed, as well as SQL Server Native Clients: 2005, 2008, 2012 installed. I may have too much installed but you never know what to keep and what to discard, some application might need it.