ERwin Data Modeler Support
The vendor does offer a forum and a knowledge base of sorts for the tool.  Plus, there is also the manual.  I don't really understand what you mean by 'everyday database admin concepts' with respect to a modelling tool, though.  Could you elaborate on that?

However, asking specific questions on data modelling tools is certainly on-topic for DBA.SE.  If you get to 'How do I do xxx in Erwin?' type of questions then it's fairly likely someone here is familiar with Erwin and can answer the questions.