If you use MCM, edit DCC settings in its page. If not, edit CharacterCreation.config.xml in the game's Modules folder.

Section 0: Debug Mode

• Debug Mode (DebugMode): turn it on if you want debug outputs. Does not require restart.
  

• Suppress Daily Tick (IgnoreDailyTick): turn it on if you don't want the game to change your weight and height.
• On a per-save basis (configuration requires MCM but may work without):
  
  • Override Age (OverrideAge): turn it on if you don't want the game to age your hero, and your hero only. Takes effect upon save load or daily tick, and does not require restart. This effectively does nothing if "Disable Auto Aging" is turned on. Note: this option seems to be bugged as of present.
  • Disable Auto Aging (DisableAutoAging): turn it on if you don't want the game to age everyone. Takes effect upon save load or hourly tick, and does not require restart.
    

• Custom Age Model (CustomAgeModel): turn it on to use DCC's age mode. If you use MCM, you need to turn it on in order to edit the following options (just tick the section divider). Will require restart. Note: conflicts with Bannerlord Tweak's age model settings.
• Infant Age Stage (BecomeInfantAge): game default is 3.
• Child Age Stage (BecomeChildAge): game default is 6.
• Teenager Age Stage (BecomeTeenagerAge): game default is 14.
• Adult Age Stage (BecomeAdultAge): game default is 18. Note: this seems to control a lot of things that will crash if the only character available is younger than this.
• Old Age Stage (BecomeOldAge): game default is 47.
• Max Age Stage (MaxAge): game default is 128.