Read the dialogue and answer the question!

Angga: What are you doing, Tyo?

Tyo: I'm fixing the wheels on my skateboard.

Angga: I will help you, if it's okay. I fixed the wheels on my skateboard yesterday.

Tyo: Thanks, but I can do it myself.

Angga: Do you know how to do it?

Tyo: Well, this is my first time.

Angga: Will you be careful? You might hurt yourself.

Tyo: Don't worry. I'm sure I can do it.

(A few minutes later)

Tyo: Ouch.

Angga: What's the matter?

Tyo: I hurt my finger. You're right. I need some help. Will you help me?

Angga: Sure. Hold the board like this.

Tyo: Okay. Thanks.

Angga: You're welcome.

What is Tyo doing?