To make things easier for them, you should do a few things beforehand. For starters, handle the initial configuration, so they won't have to worry about that. Next, make sure that you add shortcuts to useful tasks and apps on the home screen. If you've bought an Android phone for them, consider installing a simple launcher like Big Launcher or Simple Launcher. If the senior in question suffers from deteriorating eyesight, enlarging the phone's font should also be on your list of priorities.