How can I navigate to the generated sis file?

Next to resources, you should see Navigator window. If you do not see, you may add it using Window -> Show View -> Navigator. In the Navigator, (if you had packaged to default location) you should see the sis file under the root folder of your theme. You can also select the sis file in the navigator and click on Locate on Disk toolbar shortcut to open the folder containing the sis file.