“Drain energy from the Dreadnaught's weapon by breakling the channels that power it.”
This will lead you to the first power conduit that charges the super weapon. Head over to it and have Ghost Scan it. He will find a way to disable the shield that is protecting it. Once the shield is down, just start shooting the orb. Keep shooting it until it breaks.
As you approach you will see the next power conduit. Just like before, clear out the Taken around it. After that, have Ghost scan to break the shield then destroy it. Turn around and head toward the Court of Oryx. When you approach you will see some Hive appear there. You will encounter Thalnok, Fanatic of Crota with 2 Hallowed Wizards. You can attempt this fight, but a few shots in and Cayde-6 will urge you to continue on to get more Guardians on the Dreadnaught. This battle is possible but almost impossible for its challenge unless you are geared at or above the recommended Light for this mission. Head back and over to the left toward the next conduit.
Head across the next bridge. Deal with the Taken Hive that appear in front of you. Go through the opening and into the next chamber. You will find the third and final conduit for the weapon. This one behaved differently from the other two. The shield will only go down for a short period of time. You must be ready and fully loaded when you take it down to inflict as much damage as you can. Clear out the Taken in the area to make things easier. You have a Taken Wizard along with Shadow Thralls to contend with. Each time the shield comes back, so do more Taken. Always take a moment to clear out your foes before you start doing damage to the weapon core.
In the second wave, expect at least 1 Tortured Wizard. Defeat this foe and thin out the Shadow Thralls and Acolytes. Reload your weapon, have Ghost lower the shield and then open fire on the channel. The shield will stay down longer. Loose your firepower on it. Break it and then you are onto the next objective.