NEED HELP output range with Presonus Firebox

NEED HELP output range with Presonus Firebox 

I'm using my Presonus Firebox in Reaper, and I need to know how to set the "output range" to my computer speakers? Right now I have the output set to the "Main out" from Firebox to a pair of self powered Roland monitors. And that works just fine, but I cant figure out how to set the output to my computer speakers so I can use my PC speakers as monitors? Any suggestions will be much appreciated. Thanks

Hi do you only work with your laptop? in case I guess you should get a double-1/4" jack to single 1/4" jack + minijack adapter to be plugged in your laptop INPUT then open an output (maybe 3/4) in reaper in the master track you should add an hardware output to that 3/4 also I have a Firestudio with three different monitors plugged in (1-2, 3-4, 7-8) but I'm not using a laptop but it all depeneds if you're using the LT or not hope I got exactly what you need ;)