Step 1: Find clues, radio signals, note, trace information about radio frequencies
Step 2: Learn how to build a Radio Tower (Significant and VERY difficult build project)
Step 3: Make contact with new NPC survivors, form small colony.
Step 4: Deal with dialimas, random story event both in the world and some specific to the colony.
Step 5: Learn of far away city via radio tower, and the military are willing to mount a rescue but only if its worth there time.
Step 6: Meet the ridiculous requirements that the military have set
Requirements would be...
1: Colony size, number people etc
2: Health of colony, food, happiness, low illness etc etc
3: Large stockpile of weapons and ammo
4: Large number of vehicles and fuel for transporting the colony.
5: Additional supplies etc etc
And naturally while all this is happening, the zombies are attacking your colony which is not something you can just bail on anymore, various random stories, dialima, even colony members doing crazy things.
A VERY long term goal and a end state, and you have option to stay after the colony is rescued if you really are mental lol