The Road to Freedom quest in Fallout 4 will introduce you to the Railroad faction. This quest can start in a number of ways, either through investigating the Park Street Station area, overhearing people talking about the Railroad in Diamond City, or talking with Doctor Amari at the start of another quest.
Once the Road to Freedom quest pops, head over to Boston Common, or fast travel to Park Street Station if you’ve discovered it. When you’re there you’ll see a Protectron, go ahead and speak to him and he’ll let you know about the Freedom Trail and how to follow it. Locate the fountain with the scrawled board that reads “At Journey’s End Follow Freedom’s Lantern.” If you look down onto the floor, you’ll see a Freedom Trail marker that says “A7.”
All you need to really do now is follow the red brick line along the sidewalk and around the perimeter of Boston Common. Keep following the red brick line past Massachusetts State House and you’ll see the next Freedom Trail marker “L4.” The red brick trail will next take you to the Old Granary Baking Ground and a marker “A2.” Here you’ll come across a couple feral Ghouls, make sure you’re prepared for combat here, don’t let them catch you off guard. Clear up those pesky Ghouls and carry on your trail to freedom.
You’ll pass another marker by the Old Corner Bookstore and at this point the freedom trail is about to lead you into quite a tricky confrontation with some Super Mutants, Wild Mongrels, Ghouls and Raiders. If you thought that was bad, just carry on following that line of red bricks and straight into a group of tricky Super Mutants. A handful of them have missile launchers so you’re going to want to keep on your toes and make sure you’re not vulnerable to them. You’ll also want to make sure you’re keeping your distance from the Super Mutant Suicider with a bomb under his arm. To stop yourself from being blown into tiny pieces, shoot the bomb out of his hand…or just run away!
The trail will conclude at the Old North Church, and with a marker “1R”. Have you spotted the lantern sign painted on the wall by the door? Remember what the sign said at the very start of the trail. When you head inside the church you’ll be greeted with some Feral Ghouls in the hall and lower catacombs. Simply follow the lantern markers throughout the church and downstairs to the Freedom Trail Ring.
When you come across this ring, you need to turn it so that you spell out “RAILROAD.” Once this is done, you’ll have officially completed the Freedom Trail and the Road to Freedom Quest. Now you’re ready to help out the Railroad faction.