Every triggered incident starts at your routing rules. They decide who gets notified: a teammate, a group, an on-call schedule, or an escalation policy.

Go to On-call, find the routing rules section, and click Add rule.
A rule has two parts:
Conditions — what the incident must match. You can filter on:
Add multiple conditions and choose whether the rule fires when all conditions are met or when any condition is met.
Target — who to notify when the rule matches:
Rules are evaluated in order, and you can drag them to reorder. Add one ELSE rule at the end as a fallback, so incidents that match nothing still reach someone.