Bonjour Marie Ange,
It's great that you are planning a trip to the Emerald Isle in September!
In order to get to Lough Derg, you can use public transport and a short cab ride. The
Transport for Ireland journey planner and the
Rome to Rio website are two great tools to figure that out.
Accommodation in the area can be found using this handy
search tool, or the
B&B Ireland website, should you prefer bed & breakfasts.
You might also find a tour guide that speaks your language on the
Irish Tour Guides website. I also found further information for you about Lough Derg
on their website.
I hope this helps! Please note that I can also help you in French if you prefer. Have you got planned anything else in Ireland besides a visit to St Patrick's sanctuary?
A bientôt,
Antoine