I haven't SQL2012 at my hands right now, so the mentioned steps could be a bit different. So if you can't find it at once, just look a bit around in the possibilities.

Start the "SQL Server Management" tool.

Select "SQL Express" as the engine to connect to and enter the name of the SQL instance.

If you are completely new to SQL I suggest you get a more experienced person at your side, to get you started. You can also take a look at the "Microsoft Virtual Labs". These are online virtual machines where Microsoft has a step-by-step guide to get some things done. Else start by reading a lot :-P.

You need to understand the things you do, before you do actually it.