To create a new footer:
- Access Rey Theme > Global Sections
- Hit Add new.
- Select “Footer” in the Type option.
- Publish the page
- Hit Edit with Elementor
- Add elements.

Assigning site footers globally or on a single post/page/category etc.
To assign a footer globally access Customizer > Footer > General and in the Layout select list, choose the newly created global section.
To assign a footer on an individual page or category, access its edit page (clicking on the admin bar’s Edit button) and here you should see the Page settings > Footer tab, where you can find the Layout select list, from where you can select, eg: https://d.pr/i/biekTv .