Select a DBB-bonded unit. In Unit View, tap on the DBB slot to access the Bond DBB screen.
In Bond DBB screen, tap on the Boost button at the bottom to access the Bond Level Boost screen.
IMPORTANT NOTE: Please note that the boost button is only accessible through the View Units, and Home Screens.
In the Bond Level Boost screen, the Golems, Zel, and Karma requirements will be displayed. Upon meeting the cost requirement, tap on the Boost button to get your Bond Level up!