I have removed the OIV install due to wrongfull setup if you weren't using Steam copy of the game. My apologies. 

To install simply follow this path and replace the current ces_vegetation folder mods>update>x64>dlcpacks

add <Item>dlcpacks:/ces_vegetation/</Item> to the dlclist.xml to do so follow this path mods>update>update.rpf>common>data