OPen Manage | Database and click the tables tab.
Enter the name of your new table and click create.
Click the fields tab and add the fields you want for this new table.
Click the relationships tab and you can now link this new table to other tables in relationships.
FileMaker automatically creates one layout with the same name as your table when you create it. You can pull up this layout and modify it to suit your needs and you can also create additional layouts that refer to the same table.
You may find this tutorial on "table occurrences" (those boxes found on the relationships tab) useful in getting up to speed on how they control the function of a FileMaker database: Tutorial: What are Table Occurrences?