Learn French: Tu peux modifier la coiffure pour personnaliser le personnage. - You can modify the hairstyle to customize the character.

In French, le personnage refers to a character in a story, play, or video game (like an avatar). Le caractère refers to someone's personality or nature (e.g., "He has a good character"). Since we are customizing a visual avatar here, personnage is the correct word.

Could I use changer instead of modifier here?

Yes, but they carry slightly different nuances. Modifier implies tweaking, adjusting, or altering something that already exists (like adjusting a slider for hair length). Changer often implies completely replacing one thing with another (e.g., swapping one hairstyle out for a totally different one).

How would I apply this lesson's grammar to say "to customize something new" in this sentence?

You would replace le personnage with quelque chose de nouveau. Remember that when modifying an indefinite pronoun like quelque chose or rien with an adjective, you must insert de (or d') between them, and the adjective always stays in the masculine singular.

Why use pour personnaliser rather than just the infinitive personnaliser?