Save Home Positon

Hello,
so i am in the process of calibrating my 3d printer.
Right now i try to set the home position with this instructables manual.
[www.instructables.com]

I have plugged in 3 optical endstops though they just lay around and are not mounted yet to where they should be at some point in time.
In general do i need to install them to set a home position?
Another thing.
How do i properly turn off the printer? i have the full graphic smart controller and
test it with pronterface.
Can is somehow save a homing position by software?
Is it possible for the printer to know where it stands coordinatewise each time i turn it off at a different coordinate or does it have
to search each time for the optical endstop to find its homing position?
I need to understand how that works.
Can somebody teach me more on that subject?

You need to install optical (or mechanical) endstop for each axis for sure. Usually you mount them on Xmin, Ymin and Zmin. Before each print machine will find homing position.

Ok. Thanks..... Now i understand.....