At the bottom right of the Netscape window, click on the little envelope icon, which will open up a Netscape Mail window (you should then see "Launch mail window, and check for new mail" across the bottom of the Netscape window).
OR: At the top of the Netscape window near the right, click on Window and you should see a menu drop down. From this menu, select Netscape Mail which will open up a Netscape Mail window. Then, you can click on "Get Mail" at the top left of the Netscape Mail window to read your mail.