How can I create my own course file manually?
You can manually create your course using RideWithGPS.com and then export the course's GPX Track file for use with Best Bike Split.
RideWithGPS.com has a very good help section on Creating Routes (Planning), but keep in mind that you will need a detailed map and/or turn by turn directions in order to draw an accurate course out.
Do a thorough search for the course in our system. Search the "Event/Course Name" field using a single key word for more results. For example a search using "Iron" will include results with "Iron", "Ironman", "Half-Iron", etc.
Check your event's website as they may already have a GPX Track file for download.