Can't get sound from computer to speakers

[bernisava]

I have a protools mix plus system on a g4 quicksilver. I can get the sound from the keyboards and mic to show up on the protools screen in record mode, but can't get anything to playback. I was told to go to system preferences in the sound category to set it up but it says the selected device has no input or output controls. I can only get sound to play throuh one of my speakers too when it's in the standalone mode. I went to get an adapter or something to connect from my sound card to the 888 or the behringer mixer eurorack ub802 but was told it should work through system preferences since i have the cable connecting the core card to the computer through the 888 24 i/o. I have been trying to get this system to work forever and am grateful it is at least picking up the signals now, i just need this last step to have it working properly, Although the mic is connected to a phonic t8100 preamp, I can't get it to setup in the setup window. I'm a newbie at this and it's confusing to me on how to get it all synced together. I have a motu timepiece, but i'm not using it at this point.