Here is the procedure with an associated screenshot example for step 5
Administration | Setup & Support | Blackouts
1) Create One Time or Scheduled Blackout.
2) Suspend Alarms.
3) Click the Hosts radio button and click Next.
4) In Search box, enter your desired hostname.
5) For your desired host, click each occurrence of the hostname which has a preceding + sign.
6) Make sure the "Include Child Objects.." checkbox is selected at the bottom of the screen.
7) Specify Blackout Period.
8) Provide a unique name title for the blackout.