Try downloading these files to your computer, then dragging them into Zotero from your file manager
In order of appearance the numbers represent a DOI, ISBN and arXiv ID.
Preferences> Advanced> General> OpenUrl
Pick a record (e.g. How to undertake a research project and write a scientific paper) and right-click and select "Find Available PDFs". Alternatively, use the little green arrow next to the search box at the top to get to the library look-up.
If you have to re-install word processor plug ins, information is available for Manually Installing the Zotero Word Processor Plugin