You must go on Halo Waypoint, press start and when you are in the menu press X. You should see some colored buttons. You must press the buttons from left to right with the good color. As an example, if you see a red button, a green button, 2 blue buttons and a red button, you must press B, A, X, X, B. When you did that, a forerunner keyboard. You must press every figure in order from 1 terminal, and then you have unlocked the terminal for Halo Waypoint and you will get 7000 Cr for each unlocked terminal.
NOTE: If you want to unlock it, you must have accesed it in Halo CEA or it won't work.