As you learned, Zotero is able to save references from a variety of resources and websites. There are a few important points to remember when using Zotero with Fielding's FASTsearch.
1. Saving Multiple Items
Remember, if you use the folder icon to try to save multiple items from a FASTsearch results list, you will only be saving citations and not the full-text.
Why? Zotero can only pull full-text from pages where the link to the PDF is present. Since FASTsearch is a discovery tool, it points you to the location of an article within our library, but it does not contain the article itself. Hence, the only data Zotero can grab from FASTsearch is the citation itself.
The same holds true when saving items from a Google Scholar results page.
2. How to save PDFs discovered in FASTsearch
It is certainly possible to have Zotero save the full-text PDF of a work you discovered in FASTsearch. To do so, you must take the extra step of clicking on the title of the work (in your FASTsearch results list) so you can view the record in its database.
For example, let's say I want to save item 1 in the results list shown below. I first need to click on the title:
Clicking on the title will open a new tab where I can view the article in the database in which it's stored. As long as I am on a page where the 'PDF' link for the article is present, I can use my Zotero save icon to capture the reference AND the full-text: