Under Teams go to Notification Groups as shown below and click on Add New Group. 

Give your on call group a name and click Create. Disregard teams integration for now, that will be available in a future update for more automated on call settings.

Click on the edit button next to the Schedule Group you just created. 

Add in your users from your CRM/PSA by clicking From CRM users. You can also add users from MSP Process or add them manually using the new group button. 

Search and select all users. 

Click submit once you've added them all in. 

Now go to Teams -> Scheduling and click on the team via the first drop down shown in blue below. Once it is selected click New Schedule. 

Below is an example of an on call schedule creation with notes on the screen. 

You can choose to repeat every (x) number of weeks or days. Weeks it he most common use. The starting day will be the day the schedule starts so if you want it to start on a monday, be sure to select the first monday date you would like the schedule to start. 

Period Lengh I will update the doc on later with an explanation, please use 1 for now. 

The rule range can only be set 1 year out for now but we will adjust this in the future.