dog guarding 2.5 acre land and livestock.

How do I teach my GSD 3 month to guard the 2.5 acre land from any unwanted intruder or lurker? I don't want her to necessarily bite, mostly bark bark to alert us. Her secondary kennel is outside the house next to the barn full of Pigeons, Chickens and Sheep.

I wanna make her learn the boundaries of the land she needs to protect and how to respond to an intruder.