I am designing the gravity concrete column in RAM Concrete.
How can I pinned the top and bottom of the gravity column, so that it won't attract moments?
You have only a limited control of this under Ram Concrete Analysis - Analysis Criteria. For more control of column fixity you must use lateral members.
Do you change the column fixity in RAM Frame and then that carries over to RAM Concrete?
You can assign lateral member fixity in Modeler or in Ram Frame. It does carry over to the Ram Concrete Analysis.