How do i get my av grabber pro working?

i hav bought an av grabber pro captue card and an av ps3 cable and i have downloaded the softwear and connected it but when i look at the program on the computer it comes up blank. then when i change the ps3 output setings it to av the tv goes blank and it comes up on the computer but in really back quality and going blank every few seconds. please help i dont know how to get this working and when you explain it to me make it understandable coz i am 12 years old.