You have multiple ways to search for ThreatDescriptors (and more to come -- see status here):
Search results are rendered as a table. You can view (or clone) ones you do not own, or edit ones you do:
Details are shown in a popup:
You can download query results as CSV or JSON:
Note that bulk upload is a to-be-implemented item (see status here).
Using the Create button you can upload a new descriptor, with tooltips to provide context:
When you click Edit you are able to mutate all editable attributes, with tooltips to provide context. (Note: reactions and connections are not exposed yet in the UI -- see status here.)