Your edited translation, after you press "apply" will be at the bottom of the list of translations under the "Your languages" section. Make sure that is checked and make sure the other one (the one we've provided) is unchecked.
You've also got to rebuild wyUpdate after doing this. The new translation will be inside the client.wyc file.
Also, if you want to contribute your changes we'll be happy to include them in the next version of wyBuild.