Made explicit that the user should set WEST_ROOT
@@ -234,6 +234,12 @@ WESTPA process is tarring, other cores are idle, potentially wasting CPU time.
Running the simulation
----------------------
+Make sure that the environment variable ``$WEST_ROOT`` is set and points your
+WESTPA installation. To set this variable, enter
+``export WEST_ROOT=/path/to/your/westpa/installation`` at the terminal,
+modifying the command with the appropriate path. You can check if
+``$WEST_ROOT`` is set by typing ``echo $WEST_ROOT`` at the terminal.
+
From the simulation root directory (``$WEST_SIM_ROOT``), the simulation may be
initialized using the command::
