Gather 4 wooden planks of any type
Open the crafting table
Place 2 wooden planks in the left column, middle and bottom slots
Place 2 wooden planks in the right column, middle and bottom slots
Place 2 sticks in the center column, middle and bottom slots
Take the fence gate from the result slot
Place the fence gate between two fence posts or a fence opening
Right-click or use the interact button to open and close it