uhhm ^.. so basically the next step in the DB design. You've done the ER diagram (conceptual) with some of the logical details already. So really just the next step on from that. Primary Keys, Foreign Keys, relationship constraints (1..Many, 1..1, etc) and table joins. You could perhaps make a more conceptual ER, then add the logical details to the one you have.
uhhm ^.. so basically the next step in the DB design. You've done the ER diagram (conceptual) with some of the logical details already. So really just the next step on from that. Primary Keys, Foreign Keys, relationship constraints (1..Many, 1..1, etc) and table joins. You could perhaps make a more conceptual ER, then add the logical details to the one you have.