[#1341] Added a note in ARM about cert gen

Author: msiodelski

doc/user/install.rst

@@ -1077,7 +1077,14 @@ Both the Certificate Authority key and the Certificate Authority certificate mus
 the certificate depends on the key. If they are changed, then the server key
 and certificate must also be changed.
 
-The ability to use external certificates and keys is considered experimental.
+.. note::
+
+   Imported certificates and keys must follow the same standards as those self-generated by
+   the Stork server. They must also have the same format. This
+   `ISC Knowledge Base article <https://kb.isc.org/docs/importing-external-certificates-to-stork>`_
+   provides step-by-step examples of generating a new set of certificates using OpenSSL and importing
+   them to Stork. Note that the example OpenSSL configurations from this article may have to
+   be adjusted to the specifics of your deployment.
 
 For more details, please see :ref:`man-stork-tool`.