Place the right side of the gi over the left and fold your belt in half.
Place the middle of the belt against your belly button.
Wrap both ends around your back and bring them back to the front
Bring the top end around and behind the other belt layers. Pull everything tight.
Bring the top end over the bottom end and loop it through the hole.
Pull on both ends to finish the knot.
There are other ways to tie the belt, but this is the regular/traditional way.