Review the below link for the business transaction configuration.
Also watch the below video.
I'd check out the built in business transaction "Web Page Requests" to see if that meets your needs before making a new one. You can also use that to get a good idea of what settings may be necessary if you do decide you need a new one.
I'd do some research on best practices and things like "measure explosion" (too many splittings in a business transaction that is stored in the performance warehouse) as well.