Are you talking about one for the AL or one from an outside agency? If he has Dementia he may never learn. Mom had no idea how to use the call buttons. Her alert when she was home was motion censored.
Neurologist told me that the ability to learn is lost in dementia patients. My mom has severe loss of short term memory and because short term memory is not available to be written to long term memory, her recent memory is bad too. But Mom can still learn new things after a dozen or so "learning" opportunities so she doesn't have true dementia. Mom still reads and understands what she reads so written messages can help substitute for short term and recent memory. They can also tie new things into old skill sets. I taped "HELP" labels on the panic buttons installed in her bath and bedroom and on a pendant she wore. Might work with your dad too, at least for a while. A call button is not something he is accustomed to using during his lifetime, but if he is still able to recognize when he needs help, he may push the button labeled HELP.
If an outside one, I wouldn't bother with one.