Follow object hierarchy of the database:

DBEngine - Workspace(s) - Database(s) - TableDef(s) - Field(s)

When open database, TableDefs collection contains all tables, defined in this database (including system tables, which names begin with MSys, if I remember correctly; you should skip them!). You can iterate through this collection and using Append and Delete methods you can create/delete tables into database.

Each TableDef object contains Fields collection, which contains all defined fields into table. You can iterate through this collection and using Append and Delete methods you can create/delete fields into table.

Refer MSDN for further information about working with these collections and/or methods.