Sharing access to the data in the Common Data Service. The users need permission to access the entities the app uses. To grant them access, you will need to:
1. Create a security role
2. Assign users to the security role
Note: Common Data Service for Apps has a powerful enterprise grade security model that allows you to group users in security roles and give those roles varying levels of access to entities that some of our most sophisticated business apps are built on.
Reference:
https://powerapps.microsoft.com/en-us/blog/sharing-a-canvas-app-built-on-top-of-common-data-service/ D18912E1457D5D1DDCBD40AB3BF70D5D

In Power Apps, add a data connection to an existing canvas app or to an app that you're building from scratch. Your app can connect to SharePoint, Common Data Service, Salesforce, OneDrive, or many other data sources.
Note:
Add data source
1. In the center pane, select connect to data to open the Data pane.
2. Select Add data source.
3. If the list of connections includes the one that you want, select it to add it to the app. Otherwise, skip to the next step.

4. Select New connection to display a list of connections.

5. In the search bar, type or paste the first few letters of the connection you want, and then select the connection when it appears.

6. Select Create to both create the connection and add it to your app.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/add-data-connection

Restrict access to the dataset.
Note: Another way of setting access is through manage permission in the dashboard, report, or dataset. If you share a dashboard, by default the report and the dataset will also be shared as read-only for users.
Reference:
https://radacad.com/dashboard-sharing-and-manage-permissions-in-power-bi-simple-but-useful

In Power Apps, add a data connection to an existing canvas app or to an app that you're building from scratch.
Your app can connect to SharePoint, Common Data Service, Salesforce, OneDrive, or many other data sources.
Note:
Add data source
1. In the center pane, select connect to data to open the Data pane.
2. Select Add data source.
3. If the list of connections includes the one that you want, select it to add it to the app. Otherwise, skip to the next step.

4. Select New connection to display a list of connections.

5. In the search bar, type or paste the first few letters of the connection you want, and then select the connection when it appears.

6. Select Create to both create the connection and add it to your app.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/add-data-connection

Reference:
https://docs.microsoft.com/en-us/powerapps/developer/data-platform/calculated-rollup-attributes