Once created your templates will have one or more variants (named by you) and within each variant a number of tabs which allows you to continuously change and work on each one.
In our case we have a number of variants – each one a bit different. The Gallery of photos is laid out differently from the Blog or Standard Page.
Within the Standard Page (which we are currently editing, and which is therefore not collapsed) we see:
You select each one to navigate around the panel definition. Remember to click 'update' or 'update and save' to store your changes.
This is an iterative process as you move from tab to tab – so your process/preference may be different. This is the process we find logical for us.