ckeditor for durpal 7

Hi there,

I'm looking since 2 days how to add buttons in the ckeditor in h5p for drupal 7. I'm not a developer :)  I see a lot of posts but nothing explained easily or a link to a plugin.

This link doesn't help : https://h5p.org/adding-text-editor-buttons to 'lite' for a not expert !

Please soemone could helping me ?
I just try this plugin :  https://github.com/thomasmars/h5p-add-source unfortunately it's not working

Thanks for helping