Add information on how to get the Test Adapter for Catch2.

README.md

@@ -2,6 +2,10 @@
 
 Within Visual Studio, the Test Explorer is a convenient way to run and debug unit tests. This test adapter adds support for the [Catch2 C++ test framework](https://github.com/catchorg/Catch2). This adapter is for use in combination with Visual Studio 2017.
 
+## How to get it
+
+The **Test Adapter for Catch2** is available via the [Visual Studio Marketplace](https://marketplace.visualstudio.com/items?itemName=JohnnyHendriks.ext01). It is available under the name "Catch Adapter for Catch2". The easiest way to get it is via "Extensions and Updates..." in the "Tools" menu. Of course you can also [build it yourself](Docs/Build.md).
+
 ## A Note on usage
 
  Out of the box the extension does not discover tests. You need to add settings for the **Test Adapter for Catch2** to a _.runsettings_ file and use that as your test settings. This prevents the discovery mechanism from running non-Catch2 executables in your solution upon first use.