Robert, it is necessary to write the following line in the required place of the template (php file)
<?php if( function_exists( 'fcbk_bttn_plgn_shortcode' ) ) echo
fcbk_bttn_plgn_shortcode("") ; ?>
Or you can use shortcode in the content of the page - add to the editor; more detailes can be found on the page of the plugin settings - please select the word "shortcode" in the block "Position".
If the displaying after the content of the page will be selected, then the button should automatically appear in the selected place when the settings is saved.