FrameMaker does not really work with DTDs but they have their own format (EDD = Element Definition Documents). These are F+S files that have rules analogous to DTDs plus lots of additional stuff like formatting rules. So a EDD covers what does DTD + XSL/FO + applications in XML world ...
Now you can load the DTD you did in See Fix your XML DTD.
Menu: File->Developer Tools->Open DTD
To load again: File->Developer tools->Import DTD
Here is an example, the following XML DTD entry:
<!ENTITY % Standard-attrs "Id ID #IMPLIED"><!ELEMENT Stepbystep ( Doctitle, Info?, Abstract?, Intro?, Prereq?, Steps+, Comments?, Conclusion?, Open? )><!ATTLIST Stepbystep %Standard-attrs; >
Element (Container): Stepbystep Valid as the highest-level element. General rule: Doctitle, Info?, Abstract?, Intro?, Prereq?, Steps+, Comments?, Conclusion?, Open? Attribute list Name: Id Unique ID Optional
I think it is a good policy to give some similar extension to all your FrameMaker files. [though I should probably distinguish between normal and SGML versions]. E.g. do:
File->SAVE AS xxx (e.g. Stepbystep-edd.fm
Usually, you don't need to do this, but if you imported a DTD without having defined a SGML application for it, you can catch up a little. The beginning of your EDD file must have something like this:
SGML Application: StepbystepElement (Container): StepbystepValid as the highest-level element.General rule: Doctitle, Info?, Abstract?, Intro?, Prereq?, Steps+, Comments?, Conclusion?
Now you have almost an XML editor
If everything went well you can use F+S as an XML editor for simple structured text, but before we explain this in See Create a FrameMaker Template File., let's first handle special elements (Xrefs, graphics and such) and then do some more testing