SQL Server 2012 SSRS works best with 'Business Intelligence Development Studio', which is an add on to Visual Studio 2010 for SQL Server 2012. I believe what you call it SQL Server Development Tools is the same thing now as under 'All programs' it changed it's name there but NOT when you create project. Good ole MS changing things to make it more confusing for people. You get it from Installing the advanced tools version of SQL 2012 or Enterprise or Developer edition. Everything else for developing RDL's is just a watered down version of what BIDS can do. I have no idea why at MS they did not make SQL 2012 go with VS 2012, but they did not. Every other version of SQL Server BIDS matches up with that year of VS, but 2012.
When you have BIDS, you can merely put your 'RDL' files in a location that you save to. Then say: "Add Existing" and point to the location and get all your data from them to code. If you are familiar with Report Builder that is basically a watered down version of BIDS. BIDS however maintains memory better as it is an IDE specifically created for designing SSIS, SSRS, or SSAS applications.
So if you don't have a solution, create a 'Report Project'. Make a datasource up (you need to know the database and how to connect to it or other datasource). Then go to the reports folder and choose 'Add existing' and do what I stated above. You merely find your RDL files and they will appear there.