To import a style from another page
These instructions are written as an exercise.
First style a page (P1) using CSS rules with, for example, a wrapper and headings and some text.
Using CSS rules format the wrapper width, padding, margins and text.
Format the heading in the Properties Inspector bar as h1.
Then use New CSS rule to give the heading a size or colour.
On another page (P2) have some text including some that will be the heading. Put a wrapper around it all and format the heading as h1.
With P1 open, from the CSS section select the wrapper and heading (shift+click to select all) then ctrl+click → Move CSS Rules → New Style Sheet → (give it a name) → OK (it will be saved with a .css suffix)
With P2 open choose attach icon from CSS section (looks like two links of a chain)
In File/URL box browse to your CSS rule name and also select import and OK. Your styling appears on P2.
Note that both P1 and P2 have a wrapper and a heading1. On P2 DW would not have applied the heading style if you had not formatted some words as a heading.