functional specification document

Im still working on the functional specification of the project. Im reading a lot of books to be able to figure out what way to make the diagrams and what are the important diagrams i should make. I borrowed some books from the library like database design and programming, database management systems.... Till now i made the flow duagrams for the website and im workin on the Entity relationship diagram. Im having a problem with th ERD in visio because i don't know hot to make the relations between the table. Since i still have a lot of things to do we decided that Maryam (the new member in the team) will help me with the specifications.