If your father is competant, you need to discuss this with him first, since you cannot get a DNR (do not resuscitate) [not DNA] order without his consent.
If your father is not competent to make medical decisions for himself, then you need to have a durable health care power of attourney order signed in order to make decisions on his behalf.
Then you need to talk to your father's primary care
physician and get the paperwork for a DNR signed (his doc may be required to co-sign) It is usually one page affair and doesn't take more than 10 min to do.
If your father is hospitalized, you need to have a copy of his DNR order on his chart and make sure that the staff is aware that it is in effect.
A DNR order is a guideline, not a law, so EMS services, if they are called, are not specifically obligated to honor it, if they are unaware of it's existance.
DNR order can encompass everything from no intubation
, no CPR and no drugs and all shades in between.
Make sure all your father's doctors are aware that he has a DNR order and that they have a copy for their charts.