If you’re using mobile creation, you can’t switch to Limelight and you can’t add customization. All three things you mentioned above need to be done in the portal on episodeinteractive.com, inluding publishing.
Also, mobile creation is being removed and Episode will no longer allow users to create stories directly from the app. Read this announcement: The First Change for Episode
If you want to have a Limelight story and use customization, you will have to start a new story using the portal.
To start a new story and have the limelight style, check this out!
To add the ability to customize, check this out and read the left side for instructions. Copy the template on the right side and paste it into your script.
Check out the rest of my website, dara-amarie.com for all kinds of templates and guides to help you learn how to code.