If you're using a computer that doesn't have Zotero installed, you can generate a bibliography using ZoteroBib.
ZoteroBib is a free service from the makers of Zotero. To cite a source using ZoteroBib, first copy the source's URL (or ISBN or DOI or PMID or arXiv ID or title). Then, go to zbib.org and paste it into the box.
Note: ZoteroBib is only a citation tool, and does not provide the full suite of features that Zotero provides.