Guide to creating csv files for AP520 upload

Our company is a meduim sized organization that hasn't created any EDI relationships yet. Currently we recieve very large numbers of direct pay invoices as exccel spreadsheets that take hours to manually enter into AP20. I was doing some research and found that AP520 can accept invoices converted from Non-lawson files. I have also found the excel conversion files to use but there are still vague areas in this process I dont understand and havent been able to find step-by-step instructions for. Does anyone have any experience in this area and could possibly point me in the direction of some guides or have completed this process themeselves? Thank you