isolate a track and add affects to it

how do I add effects only to one recorded voice track, not the music track as well? basically, how do I isolate a voice track and add effects to it and only it???

Select the audio that you want to apply the effect to, and apply the effect.
Details about selecting audio here: http://manual.audacityteam.org/man/audacity_selection.html

how do I isolate a voice track and add effects to it and only it???

If you have a regular mono or stereo recording (without a separate vocal track) there isn’t much you can do. If you have separate vocal & instrumental tracks (or more multi-tracks) that you recorded yourself, of course you can process the vocal track independently (before mixing).

There is a [u]Vocal Removal and Isolation[/u] effect that may work, but the results are rarely perfect.