1. Scroll over your profile picture, under Options select Switch to Salesforce Classic.
2. From the Setup, enter Service Appointment in the Quick Find box and select Field Sets under Service Appointments.
3. Click Edit next to Designated Work Fields.
4. Drag any check box field into the field set.Note You can customize a field by adding it to the service appointment object.
5. Switch back to Lightning Experience in your profile dropdown.
6. From the Field Service Admin app, click the Schedule Policies tab.
7. Click the policy where you want to enforce the designated work time slots.
8. On the Related tab, under Scheduling Policy Work Rule, click New.
9. Add the Field Service - TimeSlot Designated Work work rule to the policy.
10. Click Save.