In order to unlock LeBron in NBA 2K14, you must first complete an offline game on the All-Star difficulty or higher. After that, head to the main menu and select Options, then Features. From there, select Roster Management and scroll down to find LeBron James. Highlight him and press the A button (Xbox 360) / X button (PS3), then choose the option to add him to your active roster. That's it! You can now use LeBron in any mode while playing NBA 2K14.