After each adventure, the GM will award you XP, which you can spend to upgrade your character's attributes and skills.

• Attributes are upgraded at a rate of 50 XP per attribute point.
• Skill levels are upgraded at a rate of 10 XP per level.
• New Skills may be added at the default skill level (as per the GM) for no XP cost, then may also be upgraded at a rate of 10 XP per level.
• Magic Spells are upgraded by reducing difficulty level at a rate of 1 XP per difficulty point.
• New Spells are learned at a rate of 1 XP per spell difficulty point.

see here for Character Progression Example

PCs can also spend money to get better equipment.

In some cases, at the discretion of the GM PCs may purchase skill training from an NPC.