You need a capture card like the elgato gamecaptureHD, HDPVR2 gaming edition, or similar to stream consoles efficiently... although PS4 has built in streaming capabilities, a capture card will still stream better quality with more control. a good one will run you about 150.00
You also need streaming software like OBS. Open Broadcasting Software, then watch or read tutorials about how to use it. obs is free, xsplit is pay... your choice