on ur map editor open the map u want to edit then click the att tab
after doing that make sure u have viewattribure or something on the view dropdown option. then hold ctrl and left click the yellow parts u dont want to be there. hold down left click to drag a larger area (like on paint with pencil) but be careful as there is no cursor when u have the att button clicked so just be careful where u edit. to view the new attribute lines click zoom out then zoom back in.
hope this solves yer problem
