Have a look at our Quick Start Tutorial video Christopher - that shows you how to save a route after plotting it.
Are on on a PC or using the Mobile app?
Are you starting fresh, ie Create, Plot a Route? If so, your start point is A, so maybe it's a typo when you say (B)?
If you are in some form of Edit mode, there will be a Finish button in the top right.
Whatever, you should always be able to Save (if logged in, I think) or Download, I can't explain whybthose options wouldn't be available to you.
HTH
I know this must be very basic. I can only get started but I cannot finish. How do I end a route I am creating? I can start at a point (B), create more points (B) as I follow the route, but I have not found how to end the process.If I click I just get another (B) but having arrived at the end point of my route I cannot finish it, and go to other options such as saving or printing, or closing down without losing what I have done..