Updated a heading.

README.rst

@@ -65,8 +65,8 @@ The following steps provide guidance on how to install gprMax:
 2. Install a C compiler which supports OpenMP
 3. Build and install gprMax
 
-1. Install Python and required Python packages
-----------------------------------------------
+1. Install Python, required Python packages, and get gprMax source
+------------------------------------------------------------------
 
 We recommend using Miniconda to install Python and the required Python packages for gprMax in a self-contained Python environment. Miniconda is a mini version of Anaconda which is a completely free Python distribution (including for commercial use and redistribution). It includes more than 300 of the most popular Python packages for science, math, engineering, and data analysis.