Originally Posted By: Debolestis

I understand where to connect GND, VCC, MISO.
Does SPI-SCK goes to SCLK?
Where with SPI-CS? To MOSI?

"MISO" not used at shift register.
"Pins_Sparkfun[promicro].PNG" helps to you.
"SPI-CS" any pin, and this pin name need to set at "shift register".

Originally Posted By: Debolestis

Can I connect button matrix and shift registers together?

better don't use. but SCK/MISO/MOSI can be used for SPI and button matrix with some "magic".