When you download and install Zotero, you can add plug-ins for Microsoft Word, Google Docs, and LibreOffice. They are automatic; however, if you use LibreOffice and are having trouble, Zotero has a troubleshooting guide. This plugin allows you to add citations and a bibliography to your work automatically.
It works very similarly for each of these. Once you are ready to add citations, place your cursor where your citation should be and choose the Zotero tab at the top (or side with LibreOffice).
This will open a choice to add a citation or a bibliography.
Click on the correct choice for your task.
Citations
If you are adding a citation, a new window will open, and you will need to choose your citation type and then click OK. You will want to check 'Automatically Update Citations' as well.
Next, you will have to choose the work you are citing. The easiest way to do that is to begin typing the author's name.
When the correct work appears, you can click on it or hit the return key to select it. Then it will look like a citation.
Once you hit the return key again or click on the arrow to the right, the citation will appear in the text.
Bibliography
To add a bibliography, put your cursor where you would like your bibliography to start. Go to the same Zotero tab and choose Add/Edit Bibliography. Zotero will add all of the items that you have cited in your paper. If you update the paper, remove or add citations, the bibliography will also be updated.