Originally Posted by
ESpen36
If your dad wishes to let you use all of his miles, the easiest way is for him simply to claim awards in your name, out of his account, as often as you need them, until the account runs out.
That pretty much says it all. Also keep in mind you'll need to generate some activity in his account to keep it alive or the miles will disappear after 18 months of inactivity. If he hasn't been flying for a while, this may be something you need to focus on soon.