This is a new page for you to edit. This style page is just a simple 'sheet of A4'. The alternative With Intro
style template has areas at the top that are suited to pages that need a Table of Contents or introductory preamble, for example.
A "Format sub-heading (H3)" section heading
The above heading is created using the editor options Format / Sub-heading (H3). I recommend you DO NOT USE the Sub-heading (H2) option, for anything.
A "Format / sub-heading (H4)" section heading
The above heading is created using the editor options Format / Minor heading (H4). In all these 'heading' cases the space before and after is part of the heading definition. There is no need to add additional spacing. Some headings H2, H3 currently, have underlining which is not visible during editing (why not, I have no idea).