Skills are used to achieve things beyond the ken of a standard adventurer. Adventurers are already capable climbers, swimmers, jumpers, and combatants. (For example, Indiana Jones is just an base adventurer with skill in Archaelogy, nothing else.)
A PC can easily learn a number of skills equal to their Intelligence modifier. This is done by the PC simply saying they have done a lot of something, or specifically mentioning they are trying to figure a skill out.
Skills will be handled by using the Risus: Anything RPG game system. It's fairly easy. You have a skill (cliches in Risus terms) and when you try to do something you roll xd6 dice and add them up. The number of d6s is the rating of the skill. So if a PC has the skill Rope Use (2) they roll 2d6 when attempting to do something involving rope. Often against a static number such as 5 or 10 and trying to get equal or higher than the target difficulty. There is more nuance, but that is enough to cover the basics.
Skills start with a rating of (3) and can be increased with training during a Haven turn. Simple skills can be self-taught, but many more exotic skills must be sought after and earned from specific places or people. Once a skill is started it can usually be improved anywhere, but some exceptionally rare skills must be increased by seeking out specific teachers for improvement.