I don't think the free version supports DIRECT upload to Soundcloud, but there is an easy way to do it:
Open the song in Studio one. In the top left corner of the window, there should be a label that says "songs" next to "file" and "edit". Click on that, then from the dropdown click "export mixdown". A tab will open allowing you to decide what folder to put the song in, the song's resolution, file type, ect. HOWEVER, S1 Prime does not support exporting as MP3, which I believe is what Soundcloud needs. All you need to do is export it as some other file type (.wav works great), and then use other software to convert it to MP3. I really like Audacity for doing this, but Audacity is not just for file converting and has other menus and dropdowns to navigate, so you might have ideas for other ways you prefer to convert files with.
Hope that helps.
