Select the Debug Last Launched / Debug command [ ] to re-launch the last configuration or launch the current selection in debug mode. You can also use the keyboard shortcut F11
New in 3.3 is the ability to launch the selected resource. This feature shares the Debug Last Launched command, so when it is enabled, it in effect replaces the Debug Last Launched with the Debug command.
The preference for launching last or launching the selected resource can be changed on the Run/Debug > Launching preference page.