You'll have to level grind your way into the heavily fortified base of the aliens, build a few thousand settlements into the base, say either yes or no to everything that is asked about you, even if the NPC just asks what is your favorite color.
Weapons are composed from tube, magazine and stock and you'll have to get novice, apprentice, journeyman, expert, master and legendary tier shit in that order. Dogmeat comes out from the zero vacuum from random window to join in your conquest, culminating in final battle with the alien leader, that is just scaled up version of normal alien with few million HP, but then you get to use Liberty Prime to beat the shit out of him and then you find a time traveling machine upon there, which lets you to go back to the Pre-war era, but you manage in that way to create a stable time loop and the game ends with only "war never changes" message said by the whiny wimpy protagonist voice.