You can acquire skills through many different ways in Erinn.

For example, the Rest skill, which is the first skill available, can be simply obtained by talking to Nora at the Inn about 'Skills'.

These skills are not only useful but it also raises your EXP as well.

So, what about other skills besides the Rest skill?
Simple. You can get these the same way as the Rest skill.

Have you gone to the school and talked to Ranald?

The school is located below the Church, on the southern part of town.

I think there's even a 'Go to the School' quest.
Get this quest and go meet Ranald. He will teach you many useful things.

Teachers can also teach you different skills.
Talk to either Ranald or Lassar 'About Skills'.

So, did you get new skills?

Besides the NPCs at school, you can also get skills or find information about them by chatting with the townspeople 'About Skills'.

Sometimes, instead of giving you the skill directly, they will teach you how to get the skill.

You can use these skills to do many different things around Erinn. Try talking to as many NPCs around town to earn all different kinds of skills.