sorry if I am tottally off... it's 10 am and still no "beauty sleep"... :(
get all your instruments connected 2 a Mixer, each one on a diferent mixer channel.
press the Tab Key, now u see the back of the rack... u can now plug the mixer 2 yer soundcard's main outs (1+2). U can also plug a certain instrument directly 2 another set of outputs BUT u have 2 go into the preferences/ audio page 2 tell reason how many fisical outputs u want yer soundcard 2 use. After this all u need 2 do is plug'em .... mind u most soundcards will play what they received at channel 1+2... so 2 hear 3+4, 5+6 u'd need 2 have all yer outputs connected 2 a external mixer and then U'll b able to play/ hear them...
Don't forget the main outs are 1+2, so that's where most audio streams will play. the others are "AUXILIARY" outputs!
Hope this helps in anyway!
Z