By default, the software selects automatically the most appropriate emissions factors for the activity input you have selected, for the applicable date period, within the geographical country or address of the asset that the activity is attached to. 

To see what emissions factor was selected go to the Reports page, select "Greenhouse Gas Emissions" as the report type and run the "GHG Protocol - Audit & Verification" report. On the right-most column of that report you will see the emissions factor source, publication date, and exact document page and section.

The Emission Sources report is also a useful report that will show the emissions factor source, publication and date.