OPTION 1: Create a Wiki Page Library and Add Wiki Pages 

On the main page of your site, please click the button New and select App from the drop-down list. Find Wiki Page Library, click it and create a name for the library:

To add new pages into the library, please navigate to the Page tab and select the View All Pages button. Above the list with your pages, you will see a button New. Click it, type in a name for your new page and press Create:

NOTE: Set one of the pages as home page, if you want to use ShortPoint Theme Builder.

OPTION 2: Create Wiki or Web Part Pages in Site Pages

Open Site Contents:

Open Site Pages:

 Create a Wiki Page or a Web Part Page:

NOTE: Set one of the pages as home page, if you want to use ShortPoint Theme Builder.

OPTION 3: Create a New Page with Publishing Feature

Open Site Contents:

If you see the button Return to Classic SharePoint in the bottom left corner, please click it. Otherwise, skip this step.

Click New:

Type in a name for your new publishing page and press Create:

NOTE: Set one of the pages as home page, if you want to use ShortPoint Theme Builder.

Thank you for your attention!