Where do I go to actually use cold storage?

Sidebar → Storage → Cold Storage takes you to a file-manager-style area for your backup files. It has the familiar tools — upload, browse, share, download and delete — plus folder organization and search. It behaves like a cloud drive for your archives, which is basically what it is. If you've used the hot file manager, you'll feel at home immediately; the only real difference is what the storage is for.