To open beacons go to the recruitment panel (highlighted below), select the beacon and tap “Recruit”.
You can recruit 10 commanders at a time by tapping “Recruit x 10”. See the beacon types and their drop rates below.
Beacon types and drop rates
Recruitment Rush
When participating in a Recruitment Rush event, make sure to select the "Recruitment Event" tab in the "Recruitment" panel before using your beacons. Only Specialist Beacons can be used during this event. Learn more about Recruitment Rush here.