There are several methods of signing with Visual Studio, depending on exactly what you want to do.
For signing the compiled EXE, a post-build step is the easiest route :
In order to get a signature automatically applied to your EXE (or DLL) when you compile/build, you need to call a signing utility like SignTool.exe as a post-build step.
Microsoft has a good tutorial on that, view it here :
If you want strong name signing (at the assembly level), you'll need to re-import your certificate. Follow the procedure to export it to a file from http://codesigning.ksoftware.net/export and then re-import the certificate in to the CSP with the command:
certutil importPFX -user AT_SIGNATURE
This sets the KeySpec=2 flag (AT_SIGNATURE).
You can then re-export THAT certificate and use it directly with Visual Studio.