If you want to change the pitch, go to Edit View/Effects/Stretch and try out the buttons.
If you want to retain the pitch of your vocal, but change the tonality, go to Multitrack View. To the left of the tracks is are three buttons near the top, under the toolbar, with Vol/EQ/Bus on them. Click on the middle, EQ, button. Then right click in the "EQ" area of the track you want to change. A window with three tabs on a horizontal line, representing the EQ profile of the track, will come up. Try pushing up and pulling down on each tab while you listen to the track playing back. You will hear it become bassier, or "squeakier", or whatever.