Open Zotero.  It runs as a separate application. 

Open from your operating system's dock or file manager like any other program.

In the open Zotero Pane, find and click the Preferences option. 

1.  General:  Review and adjust as needed. 

2.  Sync:  If you have not already registered for a free account, go to  https://www.zotero.org/user/register

• Enter Username & Password 
• File Syncing items are checked. 
   

3.  Search:  Skip.  This is a more advanced option for manipulating Search results/indexes.

4.  Export:  Skip.
 

5.  Cite: 

Styles - select style you most frequently use

Word Processor - Word or LibreOffice - this should have happened automatically.  Can also re-install if necessary.

6.  Advanced: 

1.  General:   Resolver:     copy/paste >  http://resolver.ebscohost.com/openurl 

2.  Files and Folders -- Backing up is different than syncing. 
   • Consult these links for more details:
     The Zotero data directory:  https://www.zotero.org/support/zotero_data
   • How to back up your Zotero library:         Instructions from Northwestern Univ. Library
      

For more details on setting preferences - https://www.zotero.org/support/preferences