Hi Dennis! Welcome to the forum. :)
Civil registration as we know it wasn't introduced in Ireland until 1864,before that time birth certificates, marriage certificates and burial records were kept in the local parish churches.
Nenagh is a county town of Tipperary and has three record offices
. You can also have a look on the FamilySearch database
, it contains the Irish Civil Records index of births, deaths and marriages from 1845-1958.
You can find a few handy tips in this thread
too. I hope this helps!