update guide

Author: bmorelli25

docs/contribute/index.md

@@ -10,9 +10,21 @@ Whether you're a technical writer or you've only edited Elastic docs once or twi
 
 ## Contribute to the docs [#contribute]
 
-* Simple bugs and enhancements --> [Contribute on the web](on-the-web.md)
-* Complex or multi-page updates --> [Contribute locally](locally.md)
-* Test migrated content --> [Migration guide](../migration/guide/index.md)
+:::{tip}
+Starting with Elastic Stack version 9.0, Elastic documentation uses `docs-builder` to build documentation. Elastic Stack versions prior to 9.0 use our [legacy documentation build system](https://github.com/elastic/docs). The version of the docs you want to contribute to determines the tool and syntax you must use to update the docs.
+:::
+
+### Contribute to Elastic Stack version 8.x docs and earlier
+
+To contribute to earlier versions of the Elastic Stack, you must work with our [legacy documentation build system](https://github.com/elastic/docs). This system using AsciiDoc as it's authoring format.
+
+* For **simple bugfixes and enhancements** --> [Contribute on the web](on-the-web.md)
+* For **complex or multi-page updates** --> See the [legacy documentation build guide](https://github.com/elastic/docs?tab=readme-ov-file#building-documentation)
+
+### Contribute to Elastic Stack version 9.0 docs and later
+
+* For **simple bugfixes and enhancements** --> [contribute on the web](on-the-web.md)
+* For **complex or multi-page updates** --> [Contribute locally](locally.md)
 
 ## Report a bug