adding users_guide.txt

doc/source/Makefile.am

@@ -5,4 +5,4 @@
 EXTRA_DIST = api.txt CAMexample.txt Decomp.txt faq.txt Installing.txt	\
 Testing.txt base.txt c_api.txt contributing_code.txt Error.txt		\
 Examples.txt Introduction.txt mach_walkthrough.txt			\
-testpio_example.txt
+testpio_example.txt users_guide.txt

doc/source/users_guide.txt

@@ -0,0 +1,20 @@
+/*! 
+
+@page users_guide PIO User's Guide
+
+This user's guide provides information about the PIO library and
+examples on how it can be used. Please watch the PIO GitHub site
+[https://github.com/NCAR/ParallelIO] for announcements and new
+releases.
+
+ - @ref intro
+ - @ref decomp
+ - @ref error
+ - @ref test
+ - @ref examp
+ - @ref faq
+ - @ref api
+ - @ref c_api
+ - @ref contributing_code
+
+*/