Simply download the entire folder (you can delete the 'src' folder if you don't intend to build it yourself) and run the EXE. You can get it easily by clicking on the number on the right side of the screen (The one under 'Releases') and getting the zip file, extract it and boom you're done. Otherwise if you're just updating, simply click on "PapersDownloader.exe" and download to the same directory you had it in previously and replace the old one.
IMPORTANT: You NEED 2019 Microsoft Visual C++ runtimes to run this. You likely already have them, but if not click on a link to download them from an official Microsoft source:
https://aka.ms/vs/16/release/vc_redist.x64.exe (for x64 - if in doubt, use this one) https://aka.ms/vs/16/release/vc_redist.x86.exe (for x86 - if you're on 32 bit, this is likely you) https://aka.ms/vs/16/release/VC_redist.arm64.exe (for ARM64 - honestly no idea what uses ARM cores for Windows, a Surface Pro/tablet maybe?)