To find the parish you are looking for, go to the main page and you can either enter its name in the search bar:
Search for a parish by name
Or click on a county on the interactive Ireland map:
NLI Interactive Map
You can then drill down to find your parish.
Click on the name of the parish in the dialogue box and you’ll be taken to a Microfilm page.
NLI Parish Microfilm Page
Here you will see which registers are available with date ranges shown. Select a microfilm and you’ll be taken to the viewing screen:
Here you can either browse the register or use the button in the top left to filter by events (baptisms or marriages) and dates. The other buttons can be used to adjust the image (brightness, contrast, inverse). You can also print or download from here.
If you know where to look, this site is very easy to use. However, if you don’t know which parish to look in, you should try the Findmypast index.
Using the Findmypast Index
You can search the Findmypast Roman Catholic Parish register index for free, but you will need to register for a free account. Go to the search page here.
Findmypast Catholic Register search page
This page will give you several options to add additional information and hopefully you will be able to find what you are looking for. Be aware though that you may experience difficulties due to the quality of some of the source material, variable handwriting styles and the software used. So if you can locate a parish, you might have more success by browsing the registers.
For more Irish genealogy see:
Finally, as well as the John Grenham book mentioned above, you may also find these books useful: