If you are a member of a fastpath workgroup that is completely configured then the next login to spark will add a new tab to the bottom of your roster window (beside contacs and conferences). This is to be used in conjunction with the Spark Webchat for Fastpath plugin (previously enterprise only, but now open source). This will allow anyone to converse with your employees regardless of whether they have an account on your server or not.

Fastpath is intended to be used via the webchat plugin, from what i read. That user is a virtual user that is really a workgroup and a series of queues potentially. What you are trying to do is not really the intended method of use. This is why you have to do what your are attempting in a very manual process.