Hi there!
Thanks for your query.
You will find your Joomla categories for your Joomla articles. SP Page Builder pages will not under those categories. But yes, you can style the contents of your Joomla article details page with SPPB editor with the help of article integration.
Categories for Pages, are ONLY for admin purpose, they were created only to keep pages in order - not to display pages from category, as you can do with articles.
I suggest to :
- Install > Enable Article integration
- Then create articles with SPPB Mode - then you will be able to use categories, but from articles.
The following blog post may be helpfull in this case:
https://www.joomshaper.com/blog/beautify-your-joomla-blog-posts-with-sp-page-builder
https://www.joomshaper.com/documentation/sp-page-builder/sp-page-builder-4/integrations
Best Regards