How do I fix my front derailleur?
Shift into the lowest (innermost) gear. This removes the cable tension as much as possible without undoing the pinch bolt and removing the cable
Loosen the bolt that clamps the derailleur to the seat tube, rotate the clamp so the the cage is it's parallel to the chain rings, then re-tighten.
Make sure you do not move the derailleur up or down the seat tube. Usually there is a line of dirt that build up next to the clamp ring so it's easy to see the derailleur position.
You may need to re-adjust the derailleur indexing after straightening it out. The Park Tool guide walks you through that process.