Can you share the error that you get, together with the XML and the way you set up the import mapping?
Store the XML response in a string and validate the output, did you mapped the attributes correctly in the import mapping?
Probably you haven't yet defined a JSON structure and import mapping for your rest Call.
As you haven't taken any learning path of mendix I suggest you take these learning paths first
Platform basics: https://academy.mendix.com/link/paths/31/Become-a-Rapid-Developer