If your browser can run Java and is properly configured, the GoFish applet should load right up. With a fast connection this will take about 5-10 seconds.
Note: The first time you bring up GoFish you will first be presented with a Java Plug-in Security Warning dialog box alerting you to the fact that you are about to download an applet (GoFish) from Harvard University. GoFish's full functionality includes the ability to save your results to your disk; this requires you to grant explicit permission by choosing either "Grant this session" or "Grant always". This causes GoFish to be loaded as trusted software by your browser, which entails permission to write to your disk. Choosing "Deny", on the other hand, causes the GoFish to be loaded as untrusted software. You can still run it, but you will not be able to save results to disk.
To run GoFish via a web browser, it is necessary to have the Java Runtime Environment (JRE, aka Java Plugin) installed. If this is not the case, the GoFish applet will fail to load, showing (depending on the browser) either a blank page or a "broken" icon.
GoFish should be largely self-explanatory, but a brief description of how to use it may be obtained from its Help menu, or from the GoFish Help page.
A jar file including both the compiled application and source code for GoFish v1.11alpha can be obtained by clicking here. Help with downloading, unpacking and using the jar file may be found here.