From the Files overview screen you can filter your files by category (1), search for a filename (2) or filter by status, file type, last update, created date and file privacy (3). When you right click you’re presented with a set of actions for your selected files (4).
To upload new files click the Upload new files button in the top right corner (1). Keep in mind that the files will only be added to Index with this action, they won’t be linked to any Product or Catalog. If you want to upload files to a specific Product directly, you can navigate to the Product and upload the files here. Uploading and linking files simultaneously on import is also supported,read more about importing here.
To delete a file just right click the file from the overview and click Delete.