Use a dehumidifier. Paint with UGL or Sunny Dry paint once you have the moisture under control. If the walls are under outside ground level you may have to dig down and put in a French drain to re-route water problem or have a sump pump installed along the damp wall.
Use a dehumidifier to get the moisture out
Is the moisture only on the surface of the walls, or has it penetrated all the way through the sheetrock? If so, it may need to be removed completely to prevent mold growing and further damage.