Are you referring to an ofxHttp example or the oauth2 example in soundclouds api? if its the latter its here:
https://developers.soundcloud.com/docs/api/reference#token
and one might not exist in an addon so you might need an external library or to make it yourself, though I've seen OF projects interact with Twitter so im sure there is an example out there somewhere
heres an external library
https://github.com/sirikata/liboauthcpp