If you need to add a strong name to an existing Dll start VisualStudio CommandLine and use this commands:
sn -k nameOfKeyfile.snk <-- to generate a keyfile
ildasm nameOfTheDLL.dll /out:nameOfTheDLL.il <-- Get the MSIL for the DLL
ilasm nameOfTheDLL.il /dll /key=nameOfKeyfile.snk <-- Build a new DLL from the MSIL and the created KeyFile