If the turn signals do not work on either side; check to see whether the hazard flasher lights work. The turn signals and the hazard flasher use the same bulbs. If the hazard lights work; then you'll know that the bulbs are good. If the hazard flasher lights do not work, then the bulbs probably need to be replaced.
If the hazard flasher lights work, but the turn signals do not work, the problem is most likely a bad turn signal flasher unit (which is a different part than the hazard flasher unit). You can buy turn signal flashers at auto parts stores, or at the dealership.
I hope this helps!!!