To add multiple alerts to an existing case:
Open the Alerts page and filter or sort alerts as you wish. See Viewing the alerts page.
Select the alerts you want to add to a case.
Click the n Rows Selected button to the upper-right above the alerts table.
Select Add to Existing Case.
In the Add to Existing Case dialog, select a case using the drop-down menu. You can enter characters from the existing case name to help locate the case in the list.
Click Confirm.