I've missed out an important keyword. Can I add this to my resource(s) after I've published them?

You can make metadata edits at any time. From an individual resource preview, just choose ‘Edit metadata’ to review and make any changes.

To edit multiple resources at the same time, follow the steps to make a batch edit by either selecting them from your search results and clicking the blue ‘Edit selected’ box, or by adding them to a collection and choosing ‘Edit all resources’ from the collection bar.

When editing multiple resources, click on the drop down menu next to ‘Edit mode’ and select the ‘Append text/option(s)’ option to add to any existing metadata values.