This is the first real objective in the game and requires making your way through the Undead Burg and into the Undead Parish where you will fight two Bell Gargoyles:
You start by fighting the first and the second joins in shortly thereafter.
After defeating them, you can climb a long ladder and pull a switch to ring the first Bell of Awakening, which will unlock this achievement.
You can summon Solaire of Astora just outside the boss fog wall provided you are in human form.
Also note that the first gargoyle's tail can be cut off to receive a weapon needed for the Knight's Honor achievement.
As always, refer to
http://darksouls.wikidot.com for specific information relating to items or locations.