Bicycles are a common challenge when loading a truck. Most bicycles can be fitted into a load by modifying them to present a slightly flatter shape.
Try loosening the bolt that sits atop the steering column. This should allow you to turn the handlebars to the side so that they line up with the front tire. Make sure everyone knows that the handlebars are loosened so they don't hop on for a small ride and injure themselves.
You can also remove the pedals. Pay close attention to the thread direction on the pedals as they are often different on each side of the bike. If you leave them on, ensure they don't damage adjacent items.