Arduino uno shift register I have shift register 74HC595. I added 7 push buttons from Q1-7 and the 8th to ground. On the other side which pin of the register will go to Arduino pin 2? And wich one to the 5v pin?

How can I read one button at a time in the code because on the Arduino it is just 1 pin?
A shift register is an output device. You won't be able to "Read" 7 push buttons in this way. 

A shift register like that is for taking a "series" of bits on one wire and parallelizing them onto 8 wires.

It does not work in reverse. The reverse is called a multiplexer.