from the menu in the top left corner, choose which bar or pattern graphic you would like to use and click ok.
a bmp file appears in the gallery. the name of this bitmap file is the same as the name of the pattern graphic you chose.
drag that bmp file to the timeline, and edit it like any other bmp.
the image's default duration is determined by the default image length preference in the general preferences, but you can trim it or stretch it as you like, just as with any bmp file.