SVEditor provides a wizard for creating new packages. The wizard can be invoked from the main menu (File>New>SystemVerilog Package) if the SystemVerilog perspective is active or from File>New>Other>SVEditor>SystemVerilog Package.
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 package to be created. By default, the file name of the package will be packagename.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.