I've got many papers which are not on Scopus, but are picked up by Google Scholar. How do I include all those other papers into Scopus?
Scopus uses its own sources for publications in the form of publisher provided content. Their selection procedure is explained here: https://www.elsevier.com/solutions/scopus/content/content-policy-and-selection
There is no procedure to add individual documents to Scopus that I could find on their help pages. You should also be aware that it can take several weeks for a published paper to end up in Scopus. Some publishers (smaller publishers typically or new open-access publishers), conferences, technical reports might never make it to Scopus though.
On a related note, the citation count will probably lag behind Google Scholar.
It sounds like you don't understand what Scopus is. Scopus is a database of quality-curated journals and the articles published in those journals. It isn't meant to be comprehensive, and because it's quality-curated, it doesn't mean that all your papers will automatically end up in the database. Comparatively Google Scholar goes for comprehensiveness. It doesn't have a quality bar, and it'll index literally everything and anything. You should be able to find all your papers in Google Scholar, but not in Scopus.
To get your publications into Scopus, publish in a journal that's indexed by Scopus. It's as simple as that. If you've already published elsewhere, it's too late (unless the journal becomes indexed by Scopus).