You take the bobbin assembly apart by removing the two screws in the needleplate (from the top) and removing the needleplate. That will release that little finger from the slot. Take out the part and clean and oil everything. Oil everything that moves or might move on the top and bottom - the bottom cover comes off easily as does the top cover. Singer lube for the gears, both under the cover on top and on the under side. Sewing machine oil for everything else. There is a free manual online that helps with all this.