Measure the area where you wish to install the front porch railing. Purchase one based on the measurements.
Put the new railing in position. Mark the location of the mounting holes at the points where the side of the railing touches the side of the house, and where the vertical support mounting holes in the base touch the floor of the porch.
Drill 3/8-inch holes at the marked locations. If the floor of the porch is concrete, use a carbide-tipped drill to make the holes.
Insert corrosion-resistant lag bolts into the mounting holes of the rail. Screw them into the floor or wall. If your porch is concrete, use masonry screws in those locations.