Try an adhesive.
This is a simple fix. Denture adhesives, such as Super Poligrip®, are sold at local convenience stores and at a reasonable price. It only takes a small amount to secure dentures in place.
Practice good oral hygiene.
You can face the world with confidence when you know your teeth and mouth are clean. Brush regularly (the ADA recommends brushing dentures at least once daily) and soak your dentures to help prevent bad breath.