m0useanswered grow question an hour ago This site is fairly user friendly I think. But they do change things that breaks internal systems all the time.
The [+] icon in the top right corner of the page allows you to start a new diary or add weeks to existing ones. I think there is one other way to start a new one but I can't find it.
Also the mobile version of the site is not laid out well IMO. Desktop all the way.
AsNorius image is for mobile, my descrition above is for desktop.