Choose Zotero Standalone if:
Zotero Standalone runs as a separate program instead of part of your web browser.
It works with Chrome and Safari.
Download and install Zotero Standalone just as you would any other program. You will also need to install the Connectors to allow your browser to save items to your Zotero library.
Connectors allow your web browser to save citations to your Zotero library.
Open Chrome or Safari and click the Zotero Connector link for the appropriate browser to install it. This information is located at the bottom of the screen of the Zotero download page.
Each browser has its own version of the Zotero connector, so if you use both Chrome and Safari you'll need to install both.
You might need to restart Chrome or your computer for the changes to take place.