Very simple, your reseller can show you how. If you have never used Virtual Integrator it is best to have your reseller setup the import for you.  Very simple but you have to know how to do it or it could take you days while a certified consultant can do it in a matter of minutes. As for the fields you will need, manually enter an invoice in AR and note the fields you must manually enter data and in what order. Those are the fields you will need in your source file and in that order.  Once you get the source file done the consultant from your reseller can setup the job quickly.