Tamino Schema for storing a single schema?

Ok, maybe it is a newbie question, but…

How do I define a schema to save a single real W3C XML schema ? It should be a simple task but I can not get it to work although I have successfully created other Tamino schemas. Any advice?

My schema looks like the following :
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:iServices=“http://…snip…” xmlns:xs=“XML Schema” elementFormDefault=“qualified”>