Here's how to get started with Customer Audiences:
click Create Audience.
Then give the audience a name. We'll call it "Customer Phones" for this example.
You'll need to inform our system if the list you're uploading contains iOS IDFAs or Android Advertising IDs.
Additional device IDs can be added to an audience at any time, just remember to keep iOS IDFAs for iOS audiences separated from Andriod IDs for Android audiences. Currently there is no way to delete or exclude IDs from a pre-existing audience. In order to exclude device IDs, create a new audience with the unwanted IDs removed.
Note: Customer Audiences can be updated by later uploading new data into the audience, but if you have a mobile audience that requires ongoing updating, try to stick to App Action Audiences.