The container is easy to spot - but how do you get to the log? Use your marbles, and you'll have the container in hand in no time at all. :-)
Park right beside the cache - feel free to pull up along the bank on the grass beside the fence or field, to not block the lane - but don't worry too much, there are two lanes to the farm, so even if you block the lane for a few minutes, it won't be a problem.
Do NOT touch the nearby fence, and please do not try to pet the horses nor feed them anything, if they are in the nearby pasture.