Im pretty sure there are multiple topics already about where to hunt said animal.
All animals can be found either at the location of their icon or if you do the hunting quests at the outposts that you take over. If you cannot find the 'boar' animal icon on your map then you may have to do some more radio towers to unlock more of the map.
I cannot specifically tell you where to search for boar or any other animal other than that.
The only other thing I can say is if you go to the icon and cannot find any then search outside the area, sometimes they'll be up to a 100 meters away from their respective icon and sometimes you just have to leave the area and come back another time.
Just keep going with the story. I couldn't find boars either, after the initial mission that makes you kill two of them. The third radio station I got, which was right along with where the main story goes, revealed boars on the map. Sure enough, all the boars you could wish for.