I have some pre purchased my multi tickets and NSW Trainlink say that I have to validate them each time I use them.
I plan to travel from Morisset to the City and am not sure on how to validate my ticket to use it as there is no barriers or the like from what i recall at the station.
Any help greatly appreciated
Don't worry, the ticket will be validated when it goes through any barrier in the city, even though it will not be visibly marked. If you later use it on a bus the reverse will be printed with the expiry date calculated from when it was first used on rail.
Pre-purchased my-multi and pensioner excursion tickets are very convenient, I always carry a few in my wallet. The tricks are 1. Buy them anywhere except at a station because the rail-issued tickets are dated from purchase rather than from first use; and 2. Always keep the day's (or week's) ticket separately from your remaining stock. I never have to queue for the vending machine or ticket window.
Enjoy your trip!