docs: clarify jetbrains setup (denoland#9930)

Co-authored-by: Kitson Kelly <[email protected]>

docs/getting_started/setup_your_environment.md

@@ -98,7 +98,11 @@ Please report any issues.
 Support for JetBrains IDEs is available through
 [the Deno plugin](https://plugins.jetbrains.com/plugin/14382-deno).
 
-For more information on how to set-up your JetBrains IDE for Deno, read
+Once installed, replace the content of
+`External Libraries > Deno Library > lib > lib.deno.d.ts` with the output of
+`deno types`. This will ensure the typings for the extension match the current
+version. You will have to do this every time you update the version of Deno. For
+more information on how to set-up your JetBrains IDE for Deno, read
 [this comment](https://youtrack.jetbrains.com/issue/WEB-41607#focus=streamItem-27-4160152.0-0)
 on YouTrack.