By Jellyfish I am assuming you mean the self service UI that was integrated into manageIQ from the Jellyfish project.
To access that from a nightly appliance you would just go to https://yourappliance/self_service, log in, and you are good to go. If you are developing against, or want to run it from source, you will need to do the following (which is what we do in our appliance build process): https://github.com/ManageIQ/manageiq-appliance/blob/eba14e773534e3b8c998d76e17ba175886e02ec8/cfme-setup.sh#L10-L15
This will create the directory vmdb/public/self_service that is served statically when you hit https://yourappliance/self_service (and thus is not served by Rails).
If you are developing, rebuilding like that on every change is cumbersome, so you can run the gulp server locally with:
npm install # To bring in new dependencies
This will run a local server on port 3001 and automatically open a browser. Note that in this mode, it is assumed that the Rails server is running on port 3000 (which you can do with the normal
bin/rails server command). Changed made to the source are automatically reflected in the UI, so it is great for live development.
Hope that helps!