Set the first page

Hi,

I am making my first ebook and there is only one detail left that I can't find in this forum.

I would like to choose on which page the epub3 opens for the first time. I've included all the semantics to each file in Sigil and organised the table of contents in the toc.ncx, but I can't get it to open in iBooks for the first time and show the first page of the book: it goes straight to the first chapter.

Where can I configure it in Sigil?

Thank you in advance!