I need to make a link from the main menu made with a feature box to a section of the page.

Hi Lindy,

we informed about that few times, also on blog post: https://www.joomshaper.com/blog/how-to-build-onepage-layout-using-sp-page-builder (old but still current rules)

1. in that Row/Section Options add unique short name in "Section ID" field, for example, contact-me
2. Then inside menu item or addon button URL use link to that: #contact-me

you can also use absolute path to that section, with https:// domain name etc.