@6b6561 after a little further searching, this now works as intended. I just needed the first paragraph too. Thank you for pointing me in the right direction
public void playSelectedPlaylist(Context mContext, long playlist_id) {
Intent intent = new Intent(PowerampAPI.ACTION_OPEN_MAIN)
.setClassName(PowerampAPIHelper.getPowerampPackageName(mContext), PowerampAPI.ACTIVITY_STARTUP);
mContext. startActivity(intent);
PowerampAPIHelper.sendPAIntent(mContext, new Intent(PowerampAPI.ACTION_API_COMMAND)
.putExtra(PowerampAPI.EXTRA_COMMAND, PowerampAPI.Commands.OPEN_TO_PLAY)
.setData(PowerampAPI.ROOT_URI.buildUpon()
.appendEncodedPath("playlists")
.appendEncodedPath(Long.toString(playlist_id))
.appendEncodedPath("files")
.build()),FORCE_API_ACTIVITY);
}