Using Expoints
From NsdWiki
With experience comes rewards. Expoints are what allow your character to become better at whatever it is that they do. To give players the ability to intricately customize their characters, this game lacks the concepts of character classes and experience levels. Players may personalize aspects of their characters à la carte as they progress through the story using their awarded Expoints.
Some players arrive with a character concept. Others decide a direction as they go. The ins and outs of imagining, recording, and improving your character are detailed in the very next chapter, Chapter 3: Character Creation.