Hi there,
These tags usually only apply to blog posts, as they typically have an author and a post date.
Pages are a little different, as they’re static.
For example, you don’t usually see a “Written by xyz” on a regular page – this is usually reserved for blog posts, or other posts like recipes etc..
Of course, if you want to add your own tags to your post, you can add this HTML using the “Text” tab while editing your page:
<span itemprop="author" itemscope="itemscope" itemtype="http://schema.org/Person" class="author vcard">Your Name</span>