Alert group creation can be accessed from the Alert Groups page.
Here you can create an alert group which defines what actions will be taken when an alert is triggered.
Clicking on the event name will allow you to edit the event. Clicking the '+' button will allow you to add an escalation. Up to 3 escalations are allowed.
Clicking on the 'User' drop down will allow you to select a user from your company. This will be the user who gets alerted.
Clicking on any of the duration drop downs will allow you to define the time after which the user will receive the alert.
By default, the first user will have a 1 minute delay. Subsequent users will allow for a delay to be defined and that will determine the time period between when the next user will receive the alert from the previous user.