Install:
drag & drop all of the files (besides the readme.txt) into the game directory(where the RDR2.exe is stored).

Requirments:
ScriptHookRDR2 - http://dev-c.com/rdr2/scripthookrdr2/
AsiLoader - https://www.rdr2mods.com/downloads/rdr2/tools/9-rdr-2-asi-loader/