Add a description of MANAGIX_HOME to the installation docs.

A more complex description was removed as part of a previous
cleanup, but the term is still used throughout the page.

Change-Id: I519dcd1fa2c0baab2aeabbd29c2d474fc32de0bf
Reviewed-on: https://asterix-gerrit.ics.uci.edu/1500
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/asterixdb/asterix-doc/src/site/markdown/install.md b/asterixdb/asterix-doc/src/site/markdown/install.md
index fd86023..0ac954e 100644
--- a/asterixdb/asterix-doc/src/site/markdown/install.md
+++ b/asterixdb/asterix-doc/src/site/markdown/install.md
@@ -197,7 +197,9 @@
 ### Configuring Managix ###
 You will need the AsterixDB installer (a.k.a. Managix). Download the Standalone Cluster installer from [here](https://asterixdb.apache.org/download.html); this includes the bits for Managix as well as AsterixDB.
 
-To be able to create an AsterixDB instance and manage its lifecycle, the Managix requires you to configure a set of configuration files namely:
+We will refer to the directory containing the extracted files as MANAGIX_HOME and we assume that MANAGIX_HOME/bin is on your PATH.
+
+To be able to create an AsterixDB instance and manage its lifecycle, Managix requires you to configure a set of configuration files namely:
 
  * `conf/managix-conf.xml`:  A configuration XML file that contains configuration settings for Managix.
  * A configuration XML file that describes the nodes in the cluster, e.g., `clusters/local/local.xml`.