QGIS is a desktop application for that allows you to create, edit, visualise, and geospatial data.
Documentation is extensive and well organized.
Here, we will simply cover creating, styling, and publishing a QGIS project to GeoServer.
If you have not already done so, download the latesr version of QGIS from below:
Unless you have specific reasons otherwise, we recommend installing the “most stable” release
This will download the installer for your operating system and you can follow the installer instructions.