For this achievement you need to sit in the goats pen for 5 minuets without leaving. To make it easier for you I would recommend spawning before the outbreak. When you spawn head down the hill towards the crashed UFO, go passed the UFO and also the open farm and you should see a pen with lots of other goats in it on the right side. If you go into the pen it should have a pop up in the middle of your screen that says goat simulator. To get the achievement just stay in the pen for 5 minuets and after that time your achievement will pop.
If you would like to see a video guide for this I have included my guide below.