You guess the question.
No. You ask the question.
So can I Edit this code to use push buttons.
To do what?
How easy would it be.
Somewhere between trivial and damn-near-impossible. Mostly depends on your coding skills and understanding of hardware and how the loop() function gets called over and over again.
What about incrementing the units 0 to 59 on pushbuttons.
Pushbuttons don't have units.
Can anyone point me in the right direction.
Without knowing which way that would be? Sure. Turn left. Again.
Even have code for the RTC pcf8563 chip.
No. But, the very last thing you need to do is tell the chip the new time. THAT part is trivial, and is exactly the same as when getting the new time from any other source.
I have seen sketches for the DS1307 RTC, would it be eaiser to use one of those sketches?
Sure. First, you get a DS1307...