how to refresh Source data in Power Query (Excel)

it seems within PQ (Excel) my source data does not update even though my source data file is new/updated

So every Friday i download a CSV file from asoftware system and save it to a loation.... I have already set up a transformation of this file within PQ, BUT when I download a new file (updated version) and go into PQ, the 'source' data table does not update with the new data from the file...

is there a setting in PQ to 'refresh' the query with newest data file i used as original source.  how do i resolve this. i hope i made sense