You can use the Program Performance Report to review which programs led to acquiring new names. You can create smart lists and add "Person Source", using filters if you want specific smart lists for specific sources. You can also subscribe to any basic report, such as program performance report, or smart lists. Search on Welcome to Marketo Docs - Marketo Docs - Product Documentation for information on building smart lists or subscriptions.
I also recommend searching the Community for articles on Attribution Reporting if you want to dive deeper.
I need help with this again. How is a lead source report created? I found this as a legacy report and am trying to update it for my needs now. How does this standard lead source report pull the data? I would like to see the leads by month but then broken down by source per month. Is there a way to merge the two? I've searched the community and nothing is making sense to me. Please help.