Iarnród Éireann Irish Rail provide great links to Dublin city from all over the country. To plan your journey see Iarnród Éireann Irish Rail for timetables and routes.
If you are travelling by car you can book a regular or disabled car park space in the Point Village car park (€13), which is immediately beside 3Arena. Book your parking through Ticketmaster. (tickets must be pre-booked to use this car park).
You can get a taxi to the 3Arena, price will depend on distance you are travelling.
Use the Taxi Fare Estimator to determine your cost.
From Dublin City to the 3Arena is generally a 5 minute trip (traffic dependent).