How to customize CSS with Elementor (not the Pro bersion)

Hi, I am a completely beginner and I have created my home page with Elementor.
My problem is that I have organized my page with H1 H2 H3 but they have a default style given by Elementor.

Is It possible to customize my H1 H2 H3 with CSS maybe with a child theme without using the Pro version of Elementor ?

Thanks for your suggestions !