The most essential software is Python. Python 3 has been released, but I still use Python 2.7. So
would recommend you to install that. How do you get this? If you are a Linux user, Python usually comes installed. If not
use your distribution's package manager to get the 2.7 version of Python. If you are a Windows user, check out this page:
At the top of the page are listed the latest stable versions of Python 2.7 and 3. The link will take you to a download page where you need to choose your distribution.
If you would like an Integrated Development Environment (IDE), I would recommend Eric which I use in Linux. The link is
The next software is one for editing spreadsheets as all the inputs from the user are through spreadsheets saved as Comma Separated Value (.csv) files. On Windows, Microsoft Excel will do. On Linux, I use LibreOffice Calc. You can use any software as long as the software allows you to embed each cell within quotes, separate cells within a row with commas and separate lines with newline characters. Read up a little on .csv files if you want to know how to convert a .xls or similar file to .csv.
The next software you need is a plotting software. There are several but I would recommend Gnuplot. If you
are a Linux user, use your distribution package to install it as it is standard GNU software. If you are a Windows user,
it gets a bit tricky. You need to first install CygWin. You can find that here:
CygWin is an embedded Linux system within Windows. You can go all the way and install all the packages it comes with if you want to play aroundwith it. But if you just want to use it for this software, all you need is Gnuplot. In the package installer, search for Gnuplot and select it. It may happen that even after installing Gnuplot, you can't view plots because that needs Xserver installed. I would recommend that you install any Graphics based software like Xfig. Just search for Xfig in the package installer, and the dependency will be Xserver. Say yes to all the dependencies and you should be done.