Put on gloves and gather the post-hole diggers. Dig a hole 12 inches deep by 8 inches wide where the first vinyl picket fence panel will be installed.
Put one part cement and three parts masonry sand in a 5-gallon bucket. Next, take a drill and attach a paint mixer bit to the drill.
Mix the dry ingredients together thoroughly, and then moisten them incrementally with a hose until the mixture takes on a pancake batter consistency.
Set the 4-foot vinyl picket fence post in the hole and center it, making sure there is an equal space on all four sides between the ground and post.
Pour the mixed concrete into the hole, surrounding the 4-foot vinyl fence post, filling it nearly to the top. Leave a few inches unfilled to backfill the hole once the concrete dries in 24 hours.
Backfill the hole with dirt, using a shovel, once the concrete footer has dried. Next, begin to set more vinyl picket fence posts in the ground and fasten them together, following the manufacturer's instructions. The method of attachment may vary slightly, depending on the manufacturer.