code: public String upload(InputStream content) throws RedmineException {
  		final URI uploadURI = getURIConfigurator().getUploadURI();
  		final HttpPost request = new HttpPost(uploadURI);
  		final AbstractHttpEntity entity = new InputStreamEntity(content, -1);
  		/* Content type required by a Redmine */
  		entity.setContentType("application/octet-stream");
  		request.setEntity(entity);
  
  		final String result = getCommunicator().sendRequest(request);
  		return parseResponse(result, "upload",
              RedmineJSONParser.UPLOAD_TOKEN_PARSER);
  	}
docs: UPloads content on a server.
  
  @param content
  content stream.
  @return uploaded item token.
  @throws RedmineException
  if something goes wrong.