This article covers how to (re)-assign product data for multiple Products at the same time after they have been initially uploaded. For Editing data on a single Product, see this article.
Assigning Product Data
Products can be assigned a type, category, catalog, or channel after export. Simply select the product(s) and click on the ellipses (...) in the purple bottom bar that appears. Then select from the available options provided in the popup menu:
Add to Catalog:
Add to Channel:
If you need to update the product attribute data for multiple products, the fastest way is to upload a CSV with the SKU, Product Name, and updated attribute columns via the Import process in Admin > Product Settings > Import.