It's great that you want to explore this hidden gem! As Martin mentions above, the walk from the parking space is around 10 minutes, and the climb down to the actual beach (as seen on the picture) isn't difficult at all. :)
Remember that dogs aren't allowed in the field as there is cattle there, and it also mentions on the entrance gate that drones and photography for financial gain are prohibited.
Are you planning on visiting any other places in the area when you're in County Donegal? We're always here if you need more tips or suggestions, and keep us posted on your plans!