You NEED Lenny's mod loader. ( https://www.rdr2mods.com/downloads/rdr2/tools/76-lennys-mod-loader-rdr/ ) Please use other methods only when necessary as I will NOT help you if you are not using lml.

The installation is quite simple. I recommend installing all files but you may choose only the ones you like. When you open the .zip file you will be met with several folders that contain the clothing (textures, models etc.) Open each of the folders you want and select a variant if you see it. Then put all the files from that folder into the "stream" folder of LML. If you don't see a "lml" folder please, install Lenny's mod loader. If the "stream" folder is not there, you can simply create it. 