A prerequisite for creating DoDAF 2.0 projects is to have the UPDM plugin installed through MagicDraw Resource Manager/Plugin.
Other than that, creating custom model elements such as DoDAF diagrams and elements is not that much different from creating normal UML items and mostly entails simply applying stereotypes to the elements you are creating. Make sure you have loaded the custom profile into your model, and proceed from there.
Diagrams
If you want to create an OV-2 diagram, see "OV-2 Diagram". Start by specifying a target element of type Diagram and a diagram type of OV-2 Diagram. You will need the DoDAF 2.0 profile loaded and the UPDM plugin installed for this.
Operational Nodes
If you import elements of type Class and apply the Operational Node stereotype, those will be created in your model and placed on your diagrams if you so choose.
Needlines
A Needline is just a Relationship element with the Needline stereotype applied. You may create them the same way you create Relationships.