Rehydrating dried-out cigars takes a long time if you want to do it properly. Don't try to rush the process, because too much water too soon will rehydrate the leaves too quickly and will risk rupturing the wrapper and/or binder leaves as they expand.
If you have a humidor that's properly seasoned, just place them in the humidor and leave them alone for at least 4 to 6 weeks. If you don't have a humidor, place them in a tupperware container, and also place in the container a small, shallow bowl (a finger bowl works well, or a small sauce/dipping bowl). The bowl should be filled to about 1/2 capacity with distilled water (make sure it's distilled, or you will risk mold contamination). You can also use a piece of sponge or wad of paper towel soaked in distilled water, but I prefer the bowl of water. Do not let the cigars actually touch the water.
Seal the cigars in the container with the water, and let the moisture evaporate into the container. Leave the cigars in this environment for 4 to 6 weeks, opening every so often to provide fresh air and to change the water as necessary.
Rehydrated cigars will never be as good as new, but with patience and time, you can get them relatively smokable again.