If you would like break your content into several sub-pages, you need to create the sub-pages first.
Do this by selecting the three dots next to your page in the "Pages" section of the menu on the right side of your screen and selecting "Add Subpage"
Give your new page an appropriate title and make sure to save it in the correct location (probably under the page you are working on) then following the directions below.
How to Create a Link to a Page in the Wikibook
Once a page exists you can post a link to it.
Select the text you want to make a link.
In the menu where you can change the font and text size, there is a link button. Select this.
Choose the subpage you want to link to and select apply.