Update index.md

Author: ivan-hc

index.md

@@ -302,6 +302,7 @@ am -i --user topgrade
   - [How to test an installation script](https://github.com/ivan-hc/AM/blob/main/docs/guides-and-tutorials/template.md#how-to-test-an-installation-script)
   - [How to submit a Pull Request](https://github.com/ivan-hc/AM/blob/main/docs/guides-and-tutorials/template.md#how-to-submit-a-pull-request)
 - [Third-party databases for applications (NeoDB)](https://github.com/ivan-hc/AM/blob/main/docs/guides-and-tutorials/newrepo.md)
+- [BSD, freeBSD and derivative systems: configuration and troubleshooting](https://github.com/ivan-hc/AM/blob/main/docs/guides-and-tutorials/bsd.md)
 
 [Instructions for Linux Distro Maintainers](https://github.com/ivan-hc/AM#instructions-for-linux-distro-maintainers)