Once you have rung the first bell, return back to your bonfire by consuming a Homeward Bone or using the Dark Sign. You equip them using (END) If they aren't already.
It will teleport you back to Undead Parish. Spend Souls on leveling up and/or buying items before heading back up to the Cathedral.
Get to the elevator..
And step on the pressure plate in order to have it transport you back to Firelink Shrine.
Run down the stairs and get back to the shrine.
Go ahead and rest here because It will be a long and very dangerous journey ahead.
Head up the several layers of stairs into the ruins.
And go through it to the left exit.
You'll come across a massive graveyard with bones scattered about.
"Run ahead and take a right where two paths cross and quickly loot a corpse there to aquiare the Zweihandler.
When you are back at the Firelink Shrine, go up next to the sitting NPC and go down the subtle pair of stairs.
Ignore or make chitchat with the NPC's before going further on.
Keep going down.
Eventually, you'll come across an unlocked room with a huge circle in it. This is another pressure-plate activated elevator. Step on it.
Once down, go out of the tower and head right.
There will be another town right next to the one where you came from. Go up in it.
Given that you followed the beginning of this guide and picked the master key,. you should be able to open this door.
Once open, go out and cross over onto the other side of the valley by using the plank bridge.
Run into the green, moss-covered cave and keep going straight forward.
Ignore these huge ogres. They are not worth the effort.
Once you can't go forward anymore, go down this ladder.
Then the next one.
Kill the spider and go behind it. Go down.
Go forward a bit until you come across yet another ladder. Be careful If you plan on not climbing down.
If you haven't died at this point, you should see a gigantic, moving set of planks. This is a very primitive but still functional elevator. Wait until you see a bunch of planks sticking out to create a small floor..
Then jump down onto it.
It will safetly take you to the bottom of Blighttown.
Roll off the elevator to avoid the poison water and run ahead.
There will be a spider in the way. Kill it.
Keep killing spiders and run through the water before you come here.
Head into the opening and discover a bonfire. Light and rest at it.
Once rested, head back the way you came.
Just at the base of the elevator, you should be able to see a huge, white mountains with tree-ish things petruding everywhere like spikes. Run towards there.
You'll be poisoned when going through the water so pack plenty of Estus flask charges.
The huge, boulderwielding monsters will aggro as you cross the water.
When in range, they will try to smash you down by throwing the boulders at you. Keep running nonstop or get killed.
Don't bother fighting them and instead head up to the small hole in the web-covered forest.
You'll eventually enter a cave. Head inside of it.
Prepare for a boss battle, perhaps wait the poison out and go through the smoke.
You will be charged by a gigantic spider-monster. This is the Chaos Witch Quelaag, guardian of the Second Bell of Awakening.
It is a rather difficult boss due to the raw amount of HP she/it has and how It also spews out long-lasting piles of lava which you can't touch without dying.
Along with her spider parts, Quelaag also packs a mean swing with her gigantic chaos sword. It can mostly be avoided If you are in blank range of her spider jaw.
But If you stick too close to her for too long, she'll charge up a devastating massive AoE damage scream, knocking you back and causing huge amounts of HP damage.
Fighting Quelaag is all about situational awareness as Lava piles can quickly pile up and surround you in no time, leading to frequent deaths. It is also key to have your shield up and ready at all times.
Once she is defeated, head up towards the ruins of the tower in the distance.
Pull the lever..
And ring the Second Bell of Awakening.
By ringing the bells, you have awakened a sleeping giant whom now opens a certain gate for you.