You can hover over the names to get a description of what the value is. The namespace value should be something like your site name or something else unique to both your site and Facebook in general. You can't use spaces or numbers in the Namespace name though, so it'd need to be something like:
cursopreparar
I hope that helps explain what the value should be, but if you have issues setting it, just let me know.
Thanks,
Alex
Please, this fails when I set the JFB, appears:
