Warhol themeforest

Hello I am new at themeforest but I’ve asked for some help to experienced users and to WordPress Business support. So far, none of them can help me to upload images in the menu. At this stage I’ve not chosen the static home page because of this issue.

I just need to understand where and how I can upload theme to avoid the black header : https://disruptifrh.com
I will need some extra support to help me to realise and improve from where I am.
Thanks for all