In addition to the full version of Zotero, you can use ZoteroBib (also for free) to create a quick bibliography for your assignment.
ZoteroBib lacks Zotero's robust features when it comes to source management and organization, but it's a convenient way to get a head start on drafting your final bibliography. All you need are the links, ISBNs, DOIs, or other identifying information for the sources you used.
Once you've entered all your sources, you can choose your citation style, copy the draft bibliography, paste the bibliography into your assignment, and begin double checking the citations to make sure they are formatted properly.
It's important to remember that tools like ZoteroBib can save you some time, but you need to be familiar enough with the citation style you're using that you can check for ZoteroBib errors and make corrections in the bibliography.