Link Pages customazation

WordPress 4.7 with Layout-Builder theme
I would like to use the plugin WP-PageNavi but in their installation instructions is following:

In your theme, you need to find calls to next_posts_link() and previous_posts_link() and replace them.

These lines cannot be found in the layoutbuilder/sg-window theme. Would you know how to integrate WP-PageNavi in your theme?

Alternatively, would you have any suggestions how to set up page links on static pages using function wp_link_pages() and getting following options:
first | previous | 1 | 2 | … | 6 | next | last

I tried the plugin Page Links Plus which does exactly that, but PLP only has Page Links hooked to the bottom of the content. I need the links at the top (just above content) as well. This in particular to avoid that users have to scroll down the page first to be able to select, for example, the last page