First you need:
monitor(has DVI-D (HDCP) Input)
HDMI/ DVI-D (HDCP) cable
If you want hear voices you need:
cable thats other head goes to your speakers and other head to R and L audio of you'r RCA cable
Okay now place you'r HDMI and RCA cables to you'r PS3. Then place the other head of HDMI cable to your monitors DVI-D (HDCP) input. remember keep monitor and PS3 off.
Now switch your PS3 and monitor on. This kins of note should apear(in you'r language!!!)) Press yes.
Now place you'r RCA cables other head to your speakers. Now go pack to your ps3 and go to settings--->Sound settings-->First in the list-->audio input