You already have the conceptual model, which defines the relationships between the entities you're modeling. A logical model addresses the organization of data within that model, i.e. what tables and fields will actually be created and how they relate to one another (the "Relationships" diagram in MS Access is one example). Then from there you create the physical model, which is the database itself.
Depending on who you ask, the difference between a conceptual model and a logical model can be rather blurry. I prefer to keep the conceptual model on the semantic side of things, focusing on the real-world entities and their meaning; the logical model would be more syntactic, focusing on the structure of the information and some implementation details.
Does that help?
--sg
