You're going to get little community support with a version of 100 that old. Is the company unwilling to bring their software current?

You would need to take at the very least two (2) courses. Data Files which teaches you the file layouts and the BOI which teaches you about the business object interface. Yes v4.30 is ancient but it should work.

I'm with John on this one.  Push hard to get the system upgraded to a current / supported version.  While I believe BOI was technically available in v4.3, the software is a decade old, and will not run reliably on current versions of Windows.  On top of that, v4.3 was before the conversion to new Framework was finished, and I am sure what's possible in BOI would be limited accordingly.

The easiest way to create invoices is not through BOI, it is using a Visual Integrator import job.