Where to find the homepage editor?

So I am currently trying to change and modify my homepage. The first time I did it, I used sitebuilder to modify the widgets in the different boxes and build the page. I cannot seem to how I can get back to this way of modifying the front page and the only options that I am given is using the ‘customising home page’ panel on the left side of the screen which already has pre-defined sections.

I have tried going to my ‘pages’ section but cannot find the homepage there and was wondering if I’m missing something blindingly obvious?

Thanks in advance for your help!