Porto airport has a metro line (purple, line E) which runs approx. every 20 mins to Porto city centre, taking ca. 20 mins. If you are staying at Vila do Conde or Povoa de Varzim, then you can also get the metro, but you’ll first need to take the purple line two stops to Verdes, then change to the red line northbound – this will take ca. 50 mins. Alternatively, you can get a taxi (which are much cheaper than in London / Munich) or hire a rental car.