Hello bmatebo,
Log into your online account, and click on Plans and Add-ons. Several tabs will then appear. Click Change Phone Number. After you have chosen your province and city, you will be presented with 5 numbers from which to choose. Choose the one that you like the most. If none appeals to you, do not choose any, but return in a few days when the selection might be different.
Unlike some carriers, Public Mobile does not charge when a number is changed.
Good luck!