How do you prepopulate fields in XForms designer?

I have a form with the following schema:

If you look at the concept embolized arteries as below , the type is coded , but for ability to share the dictionary the concept answers are not prepopulated:

However these do not populate on the Xform designer tab. In HTML Forms, you would simply add a tag with the answer and concept ID. How do you do this in Xforms?