Blood clot loose after wisdom tooth extraction. how do i keep it in place?

Care of the clot: Keep well hydrated, don't suck, spit, rinse vigorously or allow yourself to become dehydrated. Clean it carefully.

See a dentist: If the clot is actually loose, there is no way to reattach it to the bone and most likely the clot will come out. If that happens and you start to get pain, call the dentist who extracted the tooth. If you have pain now with the loose clot, also call the doctor to be evaluated and he might be able to get a new clot to form.