The chain is fitted in the same manner as the white rope.
1 Chain goes threw the lower round ring on the headstall - the one closest to the horses chin.
2 The T piece on the end of the chain passes through the ring at the other end - tighten to ring on headstall.
3 The chain then goes round the horses neck.
4 The T piece passes through the slot in the middle of the chain, turn T piece and lock into position.
Do not use a rope to lead the horse, this is inappropriate. Use the reins from the bridle as is appropriate.
Anything else you need to know just ask, we're old hands at it.