If you only want to print the apparatus, you only need the following files provided in the STL folder.
You will need local expertise to select appropriate parameter values for the printing process.
Load them into a program such as Cura (free), which will produce a “G-code” file for your particular 3D printer.
The source files ( .SLDPRT and .SLDASM ) are proprietary formats for the SolidWorks software suite. If you do not have a SolidWorks license ( it is not free ), you can open these files with the free program eDrawings. This program allows you to view them, and export them as STL files.
(*) All 3D-print files available through an open-source license