When you start connecting multiple data sources from the same app (e.g. connecting multiple Facebook Ads accounts) on your reports, managing them can be confusing as they will have the same name as default:
In this example, we have two data sources with the same name "Facebook Insights".
To make a distinction, we can change their name.
To do it, go to your report, go to Resources - Manage added data sources and click on Edit in the data source you want to customize.
Click on the data source name that you can find in the top-left corner of the page.
Now, change the name of the data source to make it more descriptive.
Click on Done to finish.
More about managing data sources on Google Data Studio: