To join the Brotherhood of Steel in Fallout 4, players need to complete the mission 'Reunions' and head to Fort Hagen.After dealing with Kellog, players will spot a massive Brotherhood airship and receive a military radio signal for the mission 'Fire Support'.Players aid the Brotherhood Knights at the Cambridge Police Station and meet Paladin Danse, who offers the quest 'Call To Arms'.By completing missions like 'Call To Arms' and 'Semper Invicta', players can ascend through the ranks and become a member of the Brotherhood.