Insert the (numbered) battens into the mainsail. Number 1, being the top one, counting down.
1. Feed the two batten tension lines through the small hole in the batten from bottom to top. Make sure each line stays on its own side.
2. Feed both lines through the eyelet in the batten pocket from top to bottom. Make sure each line stays on its own side.
3. Push the batten forward for tension, tie the overhand knot at the same time. Just get rid of the wrinkles in the sail.
4. Finish tying with a square knot and tuck the loose ends in the batten pocket.