Item description:

You are in front of the bonfire, proceed to kneel.
1) Beat the final boss, activate the 1st ending, to Link the Fire by touching the final bonfire. That's the Link to Fire trophy down.
2) Reload save. Now beat the final boss again. This time there will be a summon sign beside the final bonfire. Activate it to summon the firekeeper and initiate the End of fire ending. That's the end of fire trophy down.