Measure the distance between the two gateposts. Subtract 1-1/2 to 2 inches from that amount to allow for the gate hardware. Divide that amount by two to find the width of each gate that you need to make.
Lay the vertical pieces of one of the gates face down on a flat work surface. Line them up and space them as you want them to appear and so they fit your measurements. Place the horizontal pieces or cross members in place across the back of the gate. Use galvanized screws to secure the pieces together. Put two screws per vertical board in the top cross member and two per board on the bottom cross member. The screws should be long enough to penetrate both boards but not so long that they go all the way through.
Measure and cut a diagonal brace piece with a circular saw. This needs to go between the lower hinge side up to the top outer edge of the gate. Attach the brace piece with galvanized screws.
Repeat Steps 2 and 3 to complete the second gate panel.
Attach the gate portion of the four hinges to the gates with screws from the hinge installation kit. Have a helper hold the gate in position while you use a carpenter's level to level the gate and get its hinge side plumb. Attach the post side of the hinges to the gate post.
Repeat Step 5 for the other gate, making sure that it's not only level and plumb with its gate post, but that it's also plumb and level with the first gate. Attach the post side of the hinges to the gate post.
Close both gates. Mark where you want to install the gate latch on one gate and the gate catch on the other. Attach the latch to one gate and the catch to the other with screws from the installation kit.
Mark where you want to install the center stop for the gate. Drive a short length of steel pipe flush with the ground at that location with a sledgehammer.
Attach the center stop to the bottom of the gate directly over the pipe with screws from the gate installation kit.