St-Valéry has no station of its own on the main French rail network — the heritage steam line that runs into town is for tourism, not transport. The practical access points are:
By car. From Paris, take the A16 motorway north to exit 24 (Abbeville), then the D40 west — about two and a half hours total. From Calais or Boulogne the drive is shorter, around an hour and a half down the A16. The town has several car parks on the edge of the centre; do not try to drive into the upper-town lanes.
By train and bus. The nearest mainline station is Noyelles-sur-Mer, on the Paris-Saint-Lazare to Boulogne line, about 6 km away. Trains from Paris take roughly two hours. From Noyelles, a local bus or taxi covers the last stretch, or you can take the heritage steam railway across the bay on certain summer schedules.
From the UK. The Eurotunnel terminal at Calais and the ferry ports at Calais, Dunkerque, and Boulogne are all within easy driving distance. St-Valéry makes a pleasant first stop for travellers heading south into France.