Just a couple of ideas for bits you could buy, I just googled them so these are just examples:
Video:
HDMI to DVI cable for your PS4 to monitor -
http://www.amazon.co.uk/Premium-HDMI-Cable-Gold-Metre-Black/dp/B000GDI6FC
Cables are pretty cheap these days so you dont need to spend a fortune.
Audio:
Optical to Analogue Convertor (optical out on the PS4 into the convertor and then analogue out of the convertor into your speakers) You will need an optical to optical cable and a phono RCA to phono RCA cable - or 3.5mm stereo jack depending on what connection your speakers have. -
http://www.amazon.co.uk/LINDY-Digit...er-White/dp/B002AKXG5E/ref=pd_sxp_grid_pt_2_2
Lindy make good kit so this should do nicely or an alternative that you find.
Hope that helps.
EDIT: Just noticed you have bought a convertor and optical cable, let us know how you get on