clarify docs

Author: SBlokhuizen

docs/source/gui.rst

@@ -282,7 +282,11 @@ This is where you set up the core parameters for NICE and provide the necessary
 This section includes settings for:
 
 * The file paths to the NICE executables for both *inverse* and *direct* modes.
-* Any environment variables that NICE requires.
+  These correspond to the executables that were built in :ref:`this section <installing_nice>`. For example:
+  ``path/to/nice/run/nice_imas_inv_muscle3`` and ``path/to/nice/run/nice_imas_dir_muscle3``
+  for the inverse mode and direct mode executable paths respectively.
+* Any environment variables that NICE requires. These are stored as a dictionary of strings.
+  For example: ``{'LD_LIBRARY_PATH': '/home/user/.local/lib'}``
 * The IMAS URIs for the machine descriptions.
 * The level of detail in the output logs generated by the solver.
 

docs/source/shape_editor_install.rst

@@ -71,8 +71,10 @@ Installing dependencies
             export LD_LIBRARY_PATH=~/.local/lib:$LD_LIBRARY_PATH
 
 
-Building the NICE inverse MUSCLE3 IMAS program
-----------------------------------------------
+.. _installing_nice:
+
+Building the NICE MUSCLE3 IMAS program
+--------------------------------------
 
 The following instructions are adapted from
 https://blfauger.gitlabpages.inria.fr/nice/install.html.