There should be a clamp on both sides of the pants, you need to open the clamps and pull the side of the pants toward your back to tighten. Some tuxedo pants have a clamp on the inside of the side of the pants. Push the clamp and pull the pant toward the back. I have known any tuxedo pants to have belt loops. If all fails, take your pants to a tuxedo company and have them show you how to tighten them.
