Once you setup Booked plugin and its settings here. You can add calendar to Elementor page builder.
First open Appointments > Shortcodes > Display the Default Calendar. Then copy [booked-calendar] shortcode.
Next open your Elementor page builder editor, select “Shortcode” widget on the left side.
Then paste shortcode to shortcode option box and click “Apply”. You will see calendar display on your Elementor page.