All graduates of TCD, and graduates of other institutions, notably DIT, who have received degrees from Trinity, and who are Irish citizens are eligible to vote. You must actually register to vote. You will not be automatically included on the register. Just because the TCD alumni association has your address does not mean that you are on the register.
Registering to vote
If you wish to vote you must register. To do this, you need to fill in this form. Then you must post it back to :-
Student & Graduate Records Team,
Trinity College Dublin,
Change of address
This a postal vote. The voting papers include full instructions for completing the ballot paper, and on returning it to Trinity.