Beading is shaped like a flower, with the head of the flower visible, and the stem between the flanges on the sheetmetal parts. Drill out the welds holding the sheet metal parts together, take out/grind out the old beading. Replace with the new beading, reassemble the sheetmetal, keeping all the sheetmetal and the beading all lined up. When everything is in line tack weld through the sheetmetal flanges and the beading.
Kevin, this takes a lot of experience and is not for the weak. Many people would not even attempt this!
Scott in CA