Go to Orders from the sidebar.
Filter the list of orders according to what registration types or products you want to see in the report. For example, from the Filters panel on the right, select your event, your specific products, date ranges, or whatever you want.
Filtering by event (example)
When the list of orders is filtered appropriately, click the green search button, then click the dropdown in the upper right, and choose either Sales by product, or Sales by variant. Then click Export.
The exported CSV report will look something like this: