SVEditor provides a wizard for creating new interfaces. The wizard can be invoked from the main menu (File>New>SystemVerilog Interface) if the SystemVerilog perspective is active or from File>New>Other>SVEditor>SystemVerilog Interface.
The wizard can also be invoked from the context menu when a container (folder or project) is selected.
At this point you will see the first dialog in the wizard.
Change the source folder if necessary. Specify the name of the interface to be created. By default, the file name of the interface will be interfacename.sv. If a different name is desired, uncheck the Default Filename check-box and change the filename. When you are done, hit Finish and review the generated code. A file header is pre-pended to the file. The header can be found in the preferences section at Window>Preferences>SVEditor>SV Template Properties.