Hi Mary, I'm not sure too many of our members would really know either. In the wild they will spend at least a few days flapping their wings to strengthen their muscles, when they feel they're ready they go! They sit in a hedge or tree for a day or so while the parents provide a gradually reducing amount of food.
Is there a wildlife rehab organisation anywhere in your area, they have the skills with knowing how to get them through each stage. Often, over here anyway, they have a lot of young birds at the same stage and they are released as a group when they're ready.