Fallout 4: Guide to Joining the Brotherhood of Steel [PS4 - Xbox One - PC]
Let's see how to join one of the factions in Fallout 4!
Guide to enter the Brotherhood of Steel
Unlike other factions in the game, joining the Brotherhood of Steel does not require you to complete particular assignments.
To get started, all you have to do is listen to the AF-95 military frequency and then pay a visit to the Cambridge Police Station. This event should trigger randomly, at some point in fact you will receive a message on the screen that will tell you to tune to that frequency. Open the Pip-Boy and under the radio tab find and select the AF-95 frequency. You will hear a message asking for help, then head to the Cambridge Police Station to begin the first Brotherhood of Steel mission.
Immediately after you can start another, "Call to Arms", which will definitively guarantee you access to the Brotherhood. All shown in this video:
As with the other factions, even in the Brotherhood of Steel after entering you can complete the optional missions offered by the faction.
BUT BE CAREFUL !!!
If you complete particular missions for other factions, the Brotherhood of Steel will become hostile towards you. In particular, this will happen if you complete the "Mass fusion" mission for the Institute faction or if you complete the "Precipice of War" mission for the Railroad.
If you want to complete all the missions of all the factions to unlock the related achievements and trophies, I therefore recommend doing a manual save before the "Mass Fusion" mission so that you can go back after completing the Institute missions and still have the chance to join the Brotherhood of Steel.