The Date Popup Timepicker module adds one more timepicker option for elements of date_popup type and date_popup widgets for date fields provided by the Date module. It uses jQuery UI Timepicker (By François Gélinas) timepicker library, and provided widget looks very similar to core's jQuery UI Datepicker widget shipped with Drupal core and utilized by the Date module.
* Dowload jQuery UI Timepicker (By François Gélinas) library from and put its content to timepicker directory inside libraries directory (usually sites/all/libraries) so you should have sites/all/libraries/timepicker directory and jquery.ui.timepicker.js and jquery.ui.timepicker.css in it.
See for more details.
* Install as you would normally install a contributed Drupal module. See for further information.
* Choose jQuery UI Timepicker option in Configuration » Date API » Date Popup