Pages
Pages are managed in Scalar's page editor. To make a new page, press the New page button at the top right of the book toolbar. To edit a page, press the Edit button while viewing that page in your book.
Every page must have a unique title. Uniqueness is important for the searchability of your page as well as providing descriptive information about your page. To help with further specificity, each page has the option to enter a description of the content found on the page. These descriptions may appear in multiple places in Scalar.
Content can be added to pages much like adding content to a blog platform like "Wordpress." Visual (WYSIWYG) and HTML views are available and the content editor allows for editing styles, alignments, headings, bullet points, etc. A single page can belong to multiple paths.
If you use Paste as plain text button, this will remove all pre-existing styles. If the text editor tries to interpret and preserve a surplus of style code, it could slow down your book and make editing tricky in the future. There is also a Paste from Word button if you have very specific formatting you do want to carry over. In addition, you can type directly into the text box.
While a knowledge of HTML is not required, its usage can help with additional customization. Much of this is trial-and-error as you work with Scalar. It can be difficult to get the exact spacing or media positioning you want.
You can also customize the default CSS at the page level or across the book. More information is the Scalar User Guide under Advanced Topics: Customizing look and feel with CSS.
When building a page, you can select from a number of Layout options that fall under three categories: General, Interactive, and Visualizations. Layout is one of the tabs below the text box, along with Relationships, Styling, Properties and Metadata.
Each layout includes a description and a small visual. Different options work better for different page types -- for example, a book splash might be a great choice for the Cover Page, while a Visual Path looks more like a visual outline of pages. Perhaps the most common Layout choice is 
"Basic" which juxtaposes text with media.
Layout options can be changed at any time, and different options can be used for each page. More information, including descriptions of the Layout options, is in the Scalar user guide in the Working with Content section.
Paths
Paths can organize the pages into linear sequence and segment content by type, theme, audience, and more.
Paths represent a linear sequence of content much like the chapters of a book. Paths can lead to other paths, other steps, and back to the home page. Any page or media file can be turned into a path by specifying the content it contains and the order in which it belongs in the linear sequence. Any time you want a reader to experience content in a specific order, use a path. When a reader arrives at a "path" they will see the content on the page as well as a list of its contents. The user can click "Begin Path" to continue to the first page of the path, or the user can click the hyperlink attached to any page on the path.
Image Credit: Alliance for Networking Visual Culture, “Flexible Structure”
To create a path: You can either make a new page or edit existing pages or media files to determine their type. From the page editor in your dashboard, click the "Relationships" tab. From the list of options, select path.
Select “To make this page a path, choose the items that it contains.”
A pop-up window will appear. Here, you should select the items you want to add to this path and then click "Add Selected." Use the drop-down list to specify whether you are adding pages, media, tags, annotations, etc. and the search field to retrieve a specific item.
You can then drag and drop those items in order to reorder them or remove them from the path as you wish.
Tags
Tags represent a non-linear grouping of content. Tags are often used as content descriptors and in Scalar they are used in much that same way, however, the tag itself is not just a bit of text, but a full-fledged piece of content. Any page or media file can act as a tag for other Scalar content. When your reader arrives at a tag they will see the information contained in the tag plus a list of items that share that same tag.
The media, “Roses,” has been tagged by three other pieces of content, “Irises,” “van Gogh,” and “Wheat Field with Cypresses,” listed below the media. Each word is a hyperlink.
To create a tag: You can either make a new page, edit existing pages, or even existing media items.
From the page editor in your dashboard, click the "Relationships" tab. From the options choose tag. Select “To make this page a tag, choose the items that it contains.”
A pop-up window will appear. From the pop-up window designate the items you want to appear as tags and then click "Add Selected."