reserving seats Heuston to Tralee
 

As a Senior how can I reserve a seat online from Heuston to Tralee.
I've searched the Irish Rail site and am unable to see how it can be done?
Do I have to make a phone call to the call centre?

Go to make the booking, ie click the fare displyed on the website and then scroll down the page and go to "Adult" and open the drop down box and click select (the fare will dissappear), then further down it gives the option to reserve seat for 3 euro.

One of the ticket options is "Reserve Seat" - just select that with no Adult/Child tickets

Many thanks guys.
Seamus