There are two types of “numbered” styles - ones which include the citation info in a footnote and ones which only include the citation info in a numbered bibliography at the end of the document (i.e. Nature, PLoS, etc.).
For the former, please insert the footnote manually, and then add the citation once the cursor is in the footnote.
W.r.t. the styles not downloading, I get the same result and have submitted feedback about it. In the meantime, here is the workaround: open notepad / or another text editor, then co to the “Code” tab on the citation style editor, copy the code there into the text file, and save it as a file with the “.csl” extension.