Clicking 'Contacts' in the top portion of the lefthand column will display all contacts in the main window. However, only about four will show. Each one takes up quite a bit of screen space. The rest require scrolling down to see. Another way to see them all: instead of using the left column, use the top menu bar item, 'Search'. A separate window opens. In its left column, click 'Contacts'.  The main window shows a compact, single line per contact list. Easier sometimes to find someone further down the list alphabetically.