Copy Paste the zip folder in your C:\..\Mafia II\pc

Open d3d9.ini
Edit line 9; EffectSearchPaths=
Your Path -> C:\..\Mafia II\pc\reshade-shaders\Shaders
Edit line 15; PresetFiles=
Your Path -> C:\..\Mafia II\pc\Mafia II.ini

https://www.dropbox.com/s/gvzt5h6pnd3o53z/Mafia_II_Reshade.zip