Once in dashboard :
[1]go to → appearance → themes → theme editor
Will automatically select the first one, called tsumugi (the other ones should work as well)
[2]scroll down to 404 template
[3] From kali craft a php-reverse-shell
[4]copy and paste in the Theme editor, save and exit
[5]set up listener on kali (nc -nvlp 1234)
[6]Trigger navigating to http://10.10.10.10/404.php (important!)