Ah, sorry I misunderstood your question.
If your files of other languages are included in your Visual Studio solution, you don’t need to do anything else to scan them. The language plugins just need to be installed on your SonarQube server, the Scanner for MSBuild will take care of the rest.
If you are scanning code outside of the context of MSBuild or a Visual Studio solution (or one of our other build-tool specific scanners, like Maven, Gradle, or Ant), usually the standalone scanner is downloaded and installed separately.
You don’t need to install any plugins for the scanner – just point it at your SonarQube instance.