After you Burn It at least once, you will gain access to the HR files which contain info on all the characters and the bonuses you can obtain from them.
Use Flair in the shop to unlock characters and earn character XP. You can also collect a Small Pack for free once every six hours. Once a character earns enough XP, they will level up and gain a permanent increase to their character ability. Unlocked characters grant massive boosts to your office.