diff --git a/README.md b/README.md
index 3a371f85100ca788770a9d39cbc78e92baf48488..0369cb7bde890c3a794136a86a649579dd3e682e 100644
--- a/README.md
+++ b/README.md
@@ -14,8 +14,9 @@ MATTA at a.matta@surrey.ac.uk
   2. [Downloading from Git Hub](#downloading-from-git-hub)
 2. [Setup](#setup)
   1. [Requirements](#requirements)
-  2. [Building NPLib](#building-nplib)
-  3. [Building NPSimulation](#building-npsimulation)
+  2. [Preparing the build](#preparing-the-build)
+  3. [Building NPLib](#building-nplib)
+  4. [Building NPSimulation](#building-npsimulation)
 3. [Benchmarks and Examples](#benchmarks-and-examples)
   1. [Benchmarks](#benchmarks)
   2. [Examples](#examples)
@@ -52,6 +53,15 @@ In order to compile NPSimulation, a recent installation of Geant4 (tested
 with version 9.6 and 10.1) is needed. If you want to use GDML format in 
 NPTool, Geant4 should be installed with GDML support.
 
+### Preparing the build
+To set the needed environment variables, PATH and LD\_LIBRARY\_PATH, use
+the following convenience script and do:
+
+`source <pathname>/nptool/nptool.sh`
+
+where `<pathname>` is the location where you unpacked the NPTool package.
+Typically add these lines to your .profile or .bashrc or .tcshrc file.
+
 ### Building NPLib
 NPLib is the core of the NPTool package, holding most of the actual code. It is 
 made of a collection of stand alone C++ classes that can be used in programs 
diff --git a/README/README.md b/README/README.md
index ccc8ff56f5fd33969f2c16d4c7dc8a9a2002f57e..7a7ad28b2260087bfc158093be53cc68b2856d77 100644
--- a/README/README.md
+++ b/README/README.md
@@ -29,4 +29,4 @@ the following convenience script and do:
 
 where `<pathname>` is the location where you unpacked the NPTool package.
 
-Typically add these lines to your .profile or .bashrc or .tcshrc files.
+Typically add these lines to your .profile or .bashrc or .tcshrc file.