You will find the briefing in any job for which you have been booked. This means: you applied for the job, got accepted and then confirmed your participation in your ucm.jobs app. You can now find the briefing in that very job (click on the job in your "booked" section, scroll down). You need to read it carefully and confirm it!
In the briefing you will find all the information on how to proceed in the event of cancellations, meeting point, time, outfit, contact person on site, etc.
All upcoming jobs and the according briefings (if already posted) can be found in your app under "My Jobs" --> "Booked" section.
After you have read a briefing, you must confirm it by clicking on the button. Otherwise you will not be able to enter your check-in and check-out times. The red button indicates that you have not yet confirmed the briefing: