Gobbler and Sound Cloud are 2 different things. Gobbler is a "cloud drive" for storing data files. It does install an app on your computer that acts as a front end to this "cloud". Sound Cloud is a music hosting site - where you export a mix to so folks can play it and listen to it. This is built into SONAR and you export to Sound Cloud much like you would export to a FLAC or MP3.
Edit: I think you just get signup info for Gobbler from Cakewalk - then you get everything else you need directly from them. I did this a while ago, am not near that computer, and am conveying this from memory.
As to SoundCloud, if you do not have an audio file open, and try to export it to SoundCloud, you will get an error since as I said, SC is a music streaming site that is expecting an audio file loaded in SONAR that is then mixed down to FLAC/WAV/MP3 and then exported to SoundCloud so the public can listen to it.