As long as you are logged in and have access to financials you will find the Custom Income Report link under the Financials tab.
Getting Started:

Clicking this link will allow you to create a new report or access reports you have made historically and saved.
When creating reports we provide you with every possible user/client data field, timeline filtering, item or sellable type filter, membership filter, and more. Select the options most relevant to the report you are creating and be sure to enter a name and save the report.
When you click to generate the report it will be automatically downloaded to your computer in CSV or XLS format.