To create a newfrom within GreenHopper simply type "c" or click the Create Issue link at the top of the screen:
Enter your issue details into the Create Issue dialog box, as shown below. If you select the Create another check box (at the bottom of the screen), JIRA will create your issue and automatically pre-populate a new Create Issue dialog box with your previous issue details, while leaving the Summary field blank. This allows you to rapidly create a series of issues with similar details.
If you wish to choose which fields will appear when you create (or edit) an issue, click the Configure Fields button.
If you are using epics, you can create an issue that automatically belongs to a particular epic. See Adding an Issue to an Epic.
Screenshot: Creating an issue