~~Go to this link http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspx In the middle of the page there are links for birth, marriage or death certificates. Hit the link for the form you want. You will likely get a screen asking for a User Name and Password. (This is a program bug that the GRO has to correct). Hit cancel and the appropriate form should come up. Print the form and complete the requested information. Also provide the information from the index record--quarter/year of the event, registration district and the volume and page number where the event is recorded. Make sure you ask for a copy which costs around 4 euros. ( A cert costs closer to 20 euros). You can also ask the GRO to e-mail the copy back to you.
Just in case, you did not see my reply posted on the original query, here are the instructions.