Open your Zotero library. Open the Zotero tab in your word processor. Place the cursor where you want to add an in-text citation and click Add/Edit Citation. First off, choose your preferred citation style (you can change this later on). In the dialogue box from Zotero, search for the source that you want to cite and click Enter. If you would rather browse a list of all your references in Zotero, click on the Z button and choose Classic View. Mark the reference you wish to add and click OK.
You can add or remove information in the citations by using the citation dialogue. The dialogue opens when you add a new citation by clicking Add/Edit Citation. You can also place the cursor in an already inserted citation and click Add/Edit Citation in order to edit it.
Open the citation dialogue and click on the reference that you wish to edit. Among the alternatives showing up, Page is preselected. In the subsequent field, you can enter a page number (e.g. "1") or a page range (e.g. "1-5"). If you click on Page, you can also choose other categories of information, e.g., table, footnote, or volume.
Do not enter "p." for "page" and similar, since the reference styles will add such information automatically! ("f." and "ff." for "following" must, on the other hand, be entered manually.)
In order to add several items in the same citation, simply enter the items after one another in the citation dialogue.
Note that some reference styles sort the items automatically, e.g., in chronological order! In order to keep the order in which you have added the items, click the arrow next to the Z in the citation dialogue and untick the checkbox Keep sources sorted. You can also change the order between the items by manually clicking and dragging them into the desired place in the dialogue box.
Most reference styles include the author's name in the citations. If, however, the author is mentioned in the text preceding a reference to the same author, you normally want to avoid the name being repeated (e.g., "Smith (Smith 2021) argues that..."). In order to do this, you can check the box Suppress author in the citation dialogue. This makes Zotero exclude the author's name in the citation (e.g., "Smith (2021) argues that...").
In the field Prefix in the citation dialogue, you can enter text that is supposed to precede the source itself (e.g., "cf." in "cf. Smith 2021"). Text that is supposed to follow at the source can be entered in the field Suffix (e.g., "for a different argument" in "see Smith 2021 for a different argument").
The text entered in the field can be formatted by html tags, e.g., <i> for italics, <b> for bold, and <sub> for subscript. In order to italicise "cf.", you thus need to write "<i>cf.</i>".
Prefix/suffix are best suited when working with shorter citations in parentheses, e.g., "(Cf. Smith 2021; see also Doe 2020)". When working with more elaborate footnotes, including longer discussions, it might be easier to write the text in the document itself. See Working with footnotes.