In Kentucky, You don't need a permit to release birds into the wild. You have to have the permit to propagate bobwhites though.. so you can get a permit and raise your own, or buy your birds to release.
How you release them and at what age depends on what you are releasing them for.
If you are releasing for hunting, 16+ week olds are turned loose a few days to a few weeks before hunting.
If you want to release them for repopulating your wild quail, release 20+ week old quail that are starting to lay in the spring that has had no light or high protein feed to promote laying (meaning they will keep laying after release). May - June released birds that are 20+ weeks old will lay and set right after release. This improves the percent of your birds that will hatch out coveys.
WHAT EVER you do, make sure the stock is disease free before buying or releasing birds!! If not, you will kill what few birds you have + a BUNCH more farther than you could ever imagine!