Step 1: Download
Download the latest version of QGIS from the QGIS download page
Step 2: Install
Follow the instructions provided by the installer you downloaded.
QGIS is a program that you download onto your computer, which can be used to perform spatial operations (analyze and manipulate your data), and make composite maps.
For the Digital Humanities Research Institute, we use QGIS because it is free and open source, compared to many other tools available for macOS and Windows users.