sympl is written in Python 3. It requires a few extra Python packages, which are easily installed and available for most systems.
Sympl should work with any version of Python 3. It is usually best to install the latest stable version from www.python.org. If you already have a version of Python 3 installed and prefer not to update it, that should be OK.
You don't need all of these packages for every type of art, but you might find it easier to just install all of them to start with so you don't keep running into problems. Install the latest stable version that is compatible with your Python version.
Download Sympl from the Sympl Git release.
There is currently no installer. The Sympl source has two folders, sympl and examples. Copy those two folders directly into your working folder. Create your Python art files in the working folder.