how to show maintenance mode message in web portal

Hi Team,

I have planned a scheduled change in One Identity Manger v.8.2 and I want to display a maintenance window message in the web portal to users if anyone tries to use web portal during the change window. 

Trying to display only a blank page with website under maintenance message if anyone hits the portal url.

Kindly, let me know if there are any simple steps to achieve this.

Regards,

Sudhir