Accessing Zotero from the toolbar in Word won't work unless you have your Zotero desktop app open in the background!
From the Word toolbar, select Zotero. Then select Document Preferences -- this will open up a window where you can choose the citation style you need.
To add in-text citations in Word from the Zotero toolbar, choose Add/edit citation. A toolbar will appear in the middle of your screen. Type a keyword, author name, or title into the search bar to locate the resource you want to cite. You can add as many as you need.
Once you've located your resource(s), use the enter function of your keyboard to have create in in-text citation.
To create a bibliography from your in-text citations, simply choose Add/edit bibliography from the Zotero toolbar. A bibliography for all previously added in-text citations will appear.
You can still add in-text citations and create bibliographies with Word, even if the Zotero toolbar doesn't appear.
To create in-text citations, hold the shift key on your keyboard while dragging and dropping a resource from your Zotero desktop app into your Word document.
To create a bibliography, highlight all the resources in your Zotero desktop app that you want to cite, then drag and drop them into your Word document.