This page tells you:
When adding references:
At the References menu choose New Reference or Command + N or this icon
Choosing a reference type
Use the drop down menu at Reference Type to choose the type of reference you require. The default option is set at Journal Article. Different reference types will show different fields.
Inserting information for a reference
There are different ways to populate the Author field:
Saving a reference
To close, click on the red X at the top left corner of the window. Click Save.
Previewing your reference
Any highlighted reference will appear in the preview pane of the Library window in the selected style. To change your style click on the drop down arrow in the style box above the preview panel. References can be edited in the reference edit panel. Any PDF attachment to a reference will appear in the PDF panel.