A lot depends on how you booked the tickets in the first place. First, you can only cancel online, if you originally booked online. If you booked via an agent or by phone, then you won't be able to cancel online.
Second, you cannot have used any special discount codes that might not allow refunds.
Third, once you've picked up the tickets, you will no longer be able to cancel online.
As for tickets that you are already holding and the train has already left the station, as it were, here's how things work.
First, of course you must not have used any code that prohibits refunds.
Second, if you had purchased accomodations, then you have lost that money unless you cancelled within the time limits.
Third, the date on the ticket must be within one year of today's date.
Assuming that the above is true, then you have two options. One, a refund minus 10% of the face value. Or two, full value towards another ticket of any price or a voucher good for one year from the date of issue.