First, you need to switch on the Inventory export feature, to learn how to do so, click here. Then go to Inventory Settings section of the app, select Other from the Inventory / POS Software dropdown.
Now, click Edit next to Export Mappings. Use the list on the right hand side to assemble the fields as shown in the image below:
Save this setting and you're good to continue your Setup of Lightyear to Export to OrderMate.