after whistling something, you should be presented with the notes that the computer recognized (underneath the recording applet). It can look like that, for example:
Now, you can either go ahead and search - just hit the search button for that (see arrow).
Or, if the computer screwed up and did not accurately recognize the notes you whistled, you can manually correct them by deleting superfluous notes (hit the crossed-out note symbol) and/or moving notes around. Maybe check your corrections with the Play button, then hit Search.
If that still did not help, you might want to make another recording, maybe with better microphone settings (volume), or by singing or whistling more clearly.
The notes in this example, by the way, were extracted from this recording:
No corrections were necessary, the computer recognized the notes straight away. What I was looking for was "Der Mond ist aufgegangen", which indeed appears among the top results (for seeing these particular results, you may need to copy and paste this long URL into your browser):
http://www.musipedia.org/result.html?no_cache=1&tx_mpsearch_pi1[filtertext]=&tx_mpsearch_pi1[submit_button]=Search&opd=0-65.9-2.1/2.1-67.9-1.9/4.05-65.6-2.3/6.31-71.5-2.3/8.56-70-2.8/11.41-68-3.7/15.15-65.5-1.1
If you are still running into problems, just post the funny code that is enclosed in "audio" tags and shown underneath the recording applet (that way you make your recording available to the world) - then I can look into the problem.