To upload a clip of your tracks to your SoundCloud account, click the PROMOTION tab on the main toolbar. Under 'RELEASES', click 'Edit' next to the release you wish to upload. In the second box (under the track name), click 'SHARE'.

Next, find the box entitled 'SOUNDCLOUD' and click the bright orange 'Connect with SoundCloud' button. You'll be redirected to SoundCloud's login page asking you to allow Label Engine to access your account. Enter your credentials and click 'Connect'.