You'll notice that in your word processor, there is a new menu for Zotero. Clicking on this will bring up a sub-menu:
As you are writing your paper, when you are ready to insert an in-text citation, put the cursor where you want the citation to appear, and click on the Add/Edit Citation button. If you haven't already selected your Document Preferences (specifying the citation style you want to use), you will be prompted to select a citation style before proceeding. A search box will pop up, allowing you to search for the citation by author, title, or journal publication. When you see the citation you want to insert, click on it. If you need to add additional references in the same space, you can do another search and continue to add citations.
If you need to enter a page number, click on the citation in the Zotero box to bring up additional options.
When you are done, hit the Enter button and your citation(s) will be added to your paper.
If you are like me, you might not remember the name of the author or article you want to cite. If this is the case, you can click on "Z" symbol and choose Classic View.
This will allow you to browse your full library, including viewing your Collections folders.