You can add Tuvis Synced Messages component to Accounts, Contacts and Leads forms.
Here we are using Account as example, to do it for the other entities, you just need to change the highlighted entity "Account" for Leads or Contacts.
Go to Power Apps.
On Solutions, search for Add Tuvis Component and click on it.
On Tables, click on Account, then Forms, and click on Account
Click on Components, then More components, find Tuvis - Synced Messages click on it and drag into the layout.
For Table, select Accounts. And All Accounts for View
Then you can click on save and publish it.
Here is a videos detailing how to do it: