Hi there,
To update the featured content panel, from the dashboard, go to Appearance > Customize > Theme Options and at the bottom, under Select Featured Page, you can select the page that you want to be featured in that panel.
For more information on the Featured Panel on the Textbook Theme, please visit the Theme Page:
https://wordpress.com/theme/textbook
Let me know if you have any questions. Thanks!
Hi Darnell, thank you! The problem is with the rest of the Featured Content area, in fact I don’t see the page “Customize → Featured Content” in the menu… thanks a lot for the help!
Hmm…
What is your site URL?
I installed the theme on my self-hosted test site and was able to see Customize > Featured Content:

You’re not seeing that option as displayed in the link above? If not, do you mind providing a screenshot of what you see?
Hi Darnell, the site is hosted on “Aruba.it”, this is the URL: http://www.fondazionebianciardi.it/
On “WordPress.com”, instead, I can see Personalize > Featured content…
Hi there,
For the Featured content option to appear you’ll need to install the Jetpack plugin. More information can be found here:
https://jetpack.com/support/getting-started-with-jetpack/#install-jetpack