Hi, i just replied to another thread on a similar topic so just copy and pasting my ealier post.
I just arrived in Porto yesterday having flown into Lisbon. I took the Metro from the airport to the Oriente station which cost €2 for a ticket. From here I went to the 3rd or 4th floor where there is alot of small teller buildings. I was able to buy a ticket to Porto on the CP train from the ticket sales box 23/24 (I didnt arrange anything beforehand, the trains seemed to come every 30-40 minutes). The train ticket was €25 but your eligible for a decent discount if your under 25 or over 65 in age.
It was a great ride, around 3 hours and it stopped around 4 times. Very comfortable and loads of space to store your bag above you in the shelves (nice and close). On your ticket is shows your selected carriage number and seat number which was relatively easy to locate once on the train. The ticket sales person was extremely helpful and talked me through how to exactly to take the train.
I got off at the Porto Campanha station. It was the last stop, the PA did announce the stops in english so its easy to make sure you get off at the right stop. I took the nearby train to the Sāo Bento train station which was closer to my hotel and the travel was included in my train ticket already.
Hopefully this helps! I begin my first Camino this Monday 10th and can’t wait.
Gracie