If you use a tool that supports connecting to OData v4 data sources, you can connect to the URL https://webapp.brightmetrics.com/OData.ashx
If you are exporting data from an individual report directly, not using OData, the URL for each individual report is available in the UI.
This documentation explains how to use the API, but for the full OData specification please refer to https://www.odata.org/documentation/