Our theme comes with multiple header and footer styles. Which was built with Elementor page builder.
To use those headers/footers, you have to install and active Elementor – Header, Footer & Blocks plugin.
Then you can add/edit headers, footers from Appearance -> Header Footer & Blocks screen
When you import demo data to your site, then you will have header and footer posts like this
Aseona has 5 header and 3 footer styles. And each page has different header/footer.
If you want have only one header/footer style for your site, select your favorite one and trash others.
Edit your header/footer post to set it showing on entire website, delete exclusion rule
Then edit it with Elementor to change details with yours
For more detail on using a Elementor please read its documentation: Elementor – Getting Started