Sorry. Didn't mean to sound picky and unwelcoming. It's great to have someone else posting Irish stuff :-)

So, welcome to TMA!

When adding sites like this it's best to start with the main site - the hill in this case - and add the mound, fort and barrows as subsites of that. Be careful of creating too many levels. I would just add all the sites to the Sacred Hill site and not try to reconstruct the actual formation of the monuments by having the mound and barrows as subsites of the fort.