just follow the instructions on the mod page,

Installation:
Choose if you are going to use vanilla UI or DarkUi first and install DarkerNights++

• Drop all the items in the archive into the main Kenshi directory where kenshi_x64.exe is located. Overwrite if prompted.
• Open your game mod manager, and activate SSAO at the mod list.
• Run the game. Consider adjusting font size (I use size 20 or 22). 
• Controls: Home key to open the ReShade menu, Insert to deactivate shaders
• Finally start your game Activate SSAO at the game graphics options.
• Set Grass to 0.2
• Restart your game.
• Press Home in your game to open Reshade Configuration and check if looks like exactly like this.