Press the "Draw" button to bring up a floating image window. Use your window manager to resize it. However, be warned that there appears to be a bug in Netscape under X-Windows, where it loses X-server side memory every time you resize the window, so if you resize too many times you may have to quit and restart Netscape. The memory is not lost with the JDK standalone applet viewer, so I do not think it is a bug in NINA or a problem with Java per se. I do not know if it effects all X-servers.
A version with no floating windows designed for large screens is also available.You may want to read the instructions.