I'm an engineer working on web archival, not item collections, so this isn't my area of expertise.
That being said, the curation into collections on that level of granularity is hand-crafted by Archive employees. You'll just be uploading to one of the big community collections, then if it fits into a more specific collection, it'll be added as we curate the community-uploaded items. That can take some time given the volume of item uploads and our limited resources. My recommendation would just be to try to add as much in the way of keywords and metadata as possible.
