HowTo Display page content full width

Hello,

I use WP 4.75 with twentyseventeen theme.

I’d like to the the content of a page displayed on the full space instead of just the right part of the space. How can I do this ?

Examples : https://luc.saint-elie.com/a-propos/ or https://luc.saint-elie.com/gigs/

Thanks in advance

Luc