Operating A Stand Alone Synth Options

[helena]

Hi, i made music several times with other people, always using, unfortunately, a windows environment....
Now i decided to try and so some weird chem-lab experiments on my own on my mac g4....

Since i'm, in a way, totally new to "making music on my own" (usually i compose and sing, but do not program), i downloaded the soundforum synth,
but i cannot play it.
Do i really need a master keyboard, or some other external device (that i do not have at the moment) to operate the synth?
Can i play it from inside another application???

And, most of all, do i ABSOLUTELY NEED an externate sound card, or can i use the default one of the mac, apart from "better sound quality), just in order to start producing music?


Sorry for the very basic and "too simple" questions, but this forum is called "getting started", so....

by the way, what i need now, is to try to play this synth......

thanxxx

Helena