Impossible to put theme/demo on my WordPress

I’m with namecheap for the hosting, and I must use Softaculous WordPress to be able to have my WP-Config

But I can’t find a way to import demos on my website, the theme is stucked with the ugly one from Softaculous, do you know how I could prioritize Highend WP theme over Softaculous theme ?

Thank you

EDIT : I don’t know why but changing Softaculous theme for another Softaculous one actually fixed the problem… good ?