Do you have to write episode
S with a computer or can you use an iPad?
Both
It doesn’t matter
But I won’t let me publish
It only lets me create more episodes
As far as I know, you can only publish if you write your story within the writer’s portal on a computer, but I am newer, so I can’t be certain. 
You can write your story in the writer’s portal or on the app, but I think you have to publish it in the portal. Also, I think once you publish it, you can no longer write it on the app (but I’m not 100% sure).