For the sake of future reference, what Dr.Tank has posted is exactly right, but only applies to the older bars with the flat section of crossbrace where it meets the handlebars. For most newer bars from the bmx and moto scenes, you'll need either a stem with a fully removable face plate or you'll have to try to radically bend your stem to accept the bar, and reform it around the bars afterwards. The latter, of course, could damage your stem beyond repair, but a lot of folks have done it successfully.