The call for the academic year 2017-2018 will be published presumably by the end of July 2017and it will include all details about admission requirements and selection procedure.
The online application procedure is the only way to access the PhD programme in Civil, Environmental and Mechanical Engineering so if you are interested, please check the official website from July 2017; any news will be published here: http://web.unitn.it/en/dricam/29807/admission-and-enrollment