Hit Point recovery occurs organically with a full night’s rest of 6 or more hours.
The amount recovered depends on the conditions of rest:
Unsafe Rest (cavern, dungeon, camp, etc.): Recover 25% of your maximum HP after a full
night.
Safe Rest (inn, stronghold, etc.): Recover 25% of your maximum HP + (your Constitution
Bonus x character level) after a full night.
Downtime (one full week without adventuring): Recover all lost HP.