In the zip you download you will find a ReShade profile with .ini extension and a folder with textures and shaders (just a few actually used).
First install ReShade inside the RBR folder, than extract the content of the zip file inside the game folder, the preset should be selected by default, so as soon as you start the game it should be applied right away.
You can access the ReShade menu using the home button, with ctrl + shift + p you can switch off and on the ReShade effects.
Enjoy!