How to Unlock the First Lost Forge in Destiny 2
When you load up the game, go to Spider at the Tangled Shore and speak to him. He will give you an access card, which lets you meet with Ada-1 in the Black Armory. Go to The Tower and head towards Ikora. There should be a new path open to the right by the Ramen shop that lets you down into the annexed area of The Tower. Enter the room, trigger the cutscene, and then speak with Ada-1 when you regain control.
She will give you a quest that requires you to obtain a Weapon Core in the EDZ and kill 25 Fallen enemies. Go to the broken highway in the Outskirts and open up the cache that spawns with the Servitor Saboteur. After both steps are completed you'll need to kill both Hive enemies and get Heavy multi-kills. We suggest traveling to Mars and triggering an Escalation Protocol for this step. It's pretty easy and if you have the Heavy Ammo Finder Perk you shouldn't have an issue with getting all these kills.
For this and all the upcoming steps, we suggest using either the Thunderlord, Tractor Canon, Anarchy, One Thousand Voices, or Prospector. It's easy to get a lot of kills with these weapons, so make sure to use one if you have it. After you get all your multi-kills you'll be tasked with killing powerful enemies with a Heavy Weapon.
Either stay and grind them out in the Escalation Protocol or head to the Blind Well. My fireteam chose the latter since you can kill a ton of orange bar enemies when you use a Tier III charge. Remember, you have to be the one who secures the kill for it to count towards your progress. If you're in a fireteam, consider taking turns to make this less painless. This is probably the hardest step in the whole quest since Heavy Ammo can be rare, so just take your time and keep at it.
After you finish this step, you'll need to collect 25 Seeds that are dropped from challenging enemies. You don't need to be the one that kills the enemies, just make sure to damage them. This can be done anywhere, but if you really want to finish it load up the Strange Terrain Nightfall. In the beginning, there is a yellow bar boss that will drop anywhere from 8 to 10 Seeds per death. Just keep reloading this section until you have collected all the needed materials.
Once this is finished go back to Ada-1 and she will send you on a mission to the Volundr Forge. Complete this and you should unlock this Lost Forge activity on the EDZ. Keep in the mind more forges will unlock as the season progresses. These can be pretty difficult activities, so make sure to take the time and level up your character.