Replacing Wood Fence Posts - How to Install Them - The Spruce Apr 4, 2017 . Remove the old wood fence post. Take the rails out of the rotted wood fence post if it is still standing and set them aside. Grab the old wood fence post and wiggle it hard in all directions until it loosens. Grasp the wood fence post firmly and pull it out of the ground. If it is broken, use a shovel to remove..