The nearest railway station is in Morlaix. 

You can buy your train tickets on the SNCF website: www.voyages-sncf.com

A few travelling times: 

Paris - Morlaix (direct) : 3h50
Lyon - Morlaix (via Rennes) : 6h15
Bordeaux- Morlaix (via Paris Montparnasse) : 7h50 
  
From Morlaix to Carantec, several options :

- Taxi : Le Pors 02 98 67 00 00 et SEGALEN : 02 98 67 00 20
- Buses : Regular bus service Morlaix-Carantec-St Pol de Léon-Roscoff : http://infotransports.cg29.fr