Once you're in the Mods folder, drag and drop the mod file from the download folder to the Mods folder - or you can use cut/copy and paste commands as you prefer. Do not extract the mod zip. Just place the .zip file into your Mods folder, that's all you have to do. In the game's main menu Mod Manager, click the Reload Mods button - or else close and reopen your game. The mod should be loaded and listed in the mod manager. Congratulations on your very first modded Vintage Story Experience!