Many things affect how long it takes to recover from bypass surgery. A couple of questions--How long was your father in the hospital (is he still in the hospital)? What was his health like before the surgery; did he have other health problems? How old is he? Did the doctors say there were any problems or complications with the surgery?
From what I understand, in this part of the US where we live, most patients are in the hospital for 4 to 7 days after bypass (if the surgery goes well without any problems or complications.) They try to get the patients sitting up and then walking (first with assistance, then on their own) as soon as it is safe to do so. This helps keep them strong and helps prevent pneumonia and blood clots from forming.
What has your Dad's doctor said about how he is doing?
I have to ask why he needs help to get up, specifically. Is it because he has too much pain in his chest? does he feel mentally that his chest will be damaged from too much movement? is he generally too weak?
Your father's recovery is complicated by another condition. If the heart was the sole problem, there would be shortness of breath and/or fatigue. Did your father have a stroke (if known) and/or severe loss of blood during the surgery? Does he have any numbness of the limbs? As Yvette states, a patient should be able to walk within a few days.