How to create a photo book? There is no file tab

As @Ranjisha Sengupta has already explained, there is no dedicated "book module" in the Lightroom desktop app. However, under the Connections tab in the left-hand panel, you will see that it is possible to make a connection to Blurb. Using that connection basically uses Blurb's own BookWright tool to create a book, using a special connection to your cloud-based library where you can choose which images you want to use. 

Hi there,

Thanks for reaching out. 

A photobook can be created in Lightroom Classic. You can check the steps here: https://helpx.adobe.com/lightroom-classic/help/create-photo-book.html.

For Lightroom CC/Desktop, the feature is not yet added. You can share this idea/ feature request with us. Please feel free to create an idea/feature request on Adobe Community for other users and developers to see: https://community.adobe.com/.
We hope this helps.

Regards,

Ranjisha