Read the instructions for your latch to determine whether it mounts on the inside of the post or on the exterior planks of the fence. Hold the locking part of the latch up to the appropriate location at approximately waist height.
Hold the latch in place and use a powered screwdriver to insert the provided screws into each of the screw holes until they are flush with the top of the latch. Try to wiggle the latch to ensure that it is secure and does not move at all.
Close the gate and hold the handle and arm part up to the actual gate. Move it until is aligned perfectly with the other part of the latch on the fence, making sure the latch bar is fully engaged as it will be once installed. Place a level on top of both pieces to ensure they are even.
Insert the provided screws through each of the screw holes using a power screwdriver until the screws are flush and the latch feels secure.
Open and close the gate a few times to ensure that it functions properly.