Graphically see and modify layout

I am a total newbie to Joomla. I am running running Joomla 3.7.4 with PHP7. I have installed the Quickstart package for my template (News - refreshed). Now, where do I go to modify the page layouts? More specifically, is there a way, and if so, how, to graphically see how the modules are laid out for each page or menu option?

I really need some direction about where to go to start building the site the way I want using the template as the starting point. I haven't been able to figure it out after parsing the documentation over the past several days, mostly because the documentation seems to me to be specific to one issue or another, without a comprehensive A-to-Z how-to. Please don't think that is a complaint. I just need help getting pointed in the right direction. Thanks in advance.

Hi

Everything depends from what modfications You are trying to do. Some changes can be done in modules settings, some are possible to be done with template's settings.

For most changes I'm using override.css file (after enabling a use of it in template's settings).