To check if you are on the Electoral register follow click here

http://www.dublincity.ie/onlinevotersregistration/

If you are not currently on the register you can apply to be placed on the supplementary register.  Download and fill out the form from the link below. The form must be signed and stamped at your local Garda station, make sure you bring picture identification when attending Garda station. All applications must be received by your local authority 14 days before the date of the election. Applications in the Dublin City Council region should be sent to:

Franchise Section,

Ormond Building,

31 – 36 Ormond Quay,

Dublin 7.

http://www.checktheregister.ie/AppForms/RFA2%20English%20-%20form.pdf