Drill holes through one of the gate end-posts, if they are not pre-drilled already, at appropriate heights so the gate will hang with a clearance of 4 inches underneath. You will need two sets of two holes close together in most cases, though this will vary depending on your gate's construction.
Use the hinge plate as a template to determine where the holes should be placed.
Hold a hinge plate in place against the upper pair of holes, so that the holes in it are aligned with those in the post. Run 5-inch bolts through these holes, securing the hinge plate to the post.
Add a nut and washer to each bolt. Do the same with the second pair of holes, installing the other hinge plate.
Run hinge J-bolts through the pre-drilled holes in the gate itself and tighten the nuts. The bolts should be installed such that their bent portion points downward.
Place a ball bearing in the barrel of each hinge plate. Lift the gate and slowly lower its J-bolts into the plate barrels to complete the installation.
Grease the hinge as necessary.