If the stations have access channels, the tickets are validated as you go through the channels.
If the stations are open, you have to use one of the card readers in the station to validate your ticket.
The card readers and access channels are easy to use, just:
If you need any help, there are intercom buttons at the access channels or the ticket vending machines that put you in touch with an assistant.
You can also ask for help from any ticket clerk or Lisbon urban trains staff member.
Anyone not validating their tickets or passes after 1 October 2015 may be fined.