So to even get this questline you have to go to petra in the reef after the first "taken king" story mission and do 3 quests for her which in effect are to kill 2-3 Taken Champions on earth, then on venus, and finally on mars. These are public events so they are of course on a timer proving more time consuming than difficult.
WOLVES OF MARS:
1- after completing pre-requisite talk to petra and/or variks and she/they will send you to kill fallen on earth, moon, and venus. Its based on a percentage but it works out to approximately 300 in each place.
Earth- farm the Divide as its a small area and lots of spawns
Moon- stay in the starting area and just make a continuous loop starting with the spawn to your right as you go up the starting hill and then continuing to your right killing everiything until you make it back to the first spawn.
Venus- Ember Caves farming loop
2- to find the archon on mars head to the Rubicon Wastes then go to your left and you will see what looks like part of a ship sticking out of the dirt. Wait around this area and you will get a "the Wolves are prowling" message. Kill the subsequent waves of Wolves and on I believe wave 3 the Archon will spawn.
3- story mission on Mars "A New Den"
4- story mission on Mars "Knock Knock"
For the boss fight against the Fallen Walker you will not only be dealing with him but waves of Fallen and Cabal as well. Grab the interceptor thats to your left and then just strafe back and forth in that area attacking him and killing anything that gets close.
5- story mission on Mars "Prime's Path"
For the boss battle against the Prime on mars my best advice is Kill.The.Snipers.First. If not they will collectively take you out in short order as there are 5 of them at least. Then just keep on the run shootin the Prime when you can. You will get teleported but as long as you keep your distance and keep moving he's not too much of a problem.
I would strongly recommend being at least lv 40 *240 before starting the story missions related to this quest