Its the same process as any unity game
Download BepInEx and extract the zip on the same folder as the game .exe it should look like the one the print bellow
now open the game and after it loads the main menu close it, open the BepInEx folder and you should have several subfolders inside it now, just place the mod dll file from Sangmer inside the PLUGINS folder and your should be ready to go
HOW TO USE BEPINEX
Cause there are a lot of people asking how to use BepInEx and it is a little much to go looking through all of the pile of responses with BepInEx in it, so doing this to make it easier to find. Same process for the complex breeding mod