Disney 12 inch bicycle handle bar cant figure out

SOURCE: how to raise the handle bar in huffy 14

The silver bolt on the neck behind the handlebars. Losen it off a few turns, and the entire stem can be raised and lowered. Be sure not to raise it too much, should be a minimum mark, or else leave a good inch or two still in the frame, and tighten it back up. Make sure it's aligned with the front wheel though!

SOURCE: how do we keep up the handle bars

If the handlebars are "slipping" then you need to tighten the bolts on the stem. The stem is the piece that connects the handlebar to the bike itself and usually has 1, 2 or 4 hex headed bolts that hold the handlebar in place. The Park Tool website indicates that you should torque these bolts to 15-20 foot lbs. This is important because the potential for injury is high if the bars slip at the wrong time. If you don't have a torque wrench then take the bike to your local bike shop and let a professional with the proper tool do the work. This is so simple and quick a fix that they may not even charge you