I would concentrate on converting the parts of the application that work with the data first. You probably already have a project. If not I would set up a new project by typing the following in the command window:

create project new_big_app

Under the code page tab of the project window, I would add my startup program. Then I would rebuild the project. This will pull your application, as it currently stands, into the project. You may receive many window dialogs asking you to locate programs, reports, databases, etc. After the rebuild you should have a functional project with paths to each component that makes up the app. When you run the rebuild be sure the display errors check box is check. A file of all error will be created with the same name as the project except with an .err extension. Check the file for error as follows:

modify command new_big_app.err

Resolve all error until you can build the project error free.

You are probably working with free tables. You will no doubt want to eventually move tables that have a logical parent child relationship to a database container and take advantage of things like persistent relations, table buffering, referential integrity, transactional processing, and to a limited extent a data dictionary. To create a database container type the following in the command window

modify database new_big_app

A window will open. Right click in the window for a menu. Select Add table and pull all tables used on a day to day basis into the Database Container (DBC). Arrange the tables in logical order. With drag and drop techniques select the primary keys of parent tables and pull them over to the child tables and drop them into the child's corresponding related key. After you have all relevant tables in the DBC, and the relationship between parent and child tables defined, right click in the DBC window and select Edit Referential Integrity from the menu that appears. Complete the dialogs that follows and presto, you will have a DBC with persistent relations, transaction processsing capabilities, referential intregrity checking, and a limited data dictionary. After completion of building the project and creating the DBC, check back.