Draw one manuscript with a collaborator, each on your own Mac or iPad.
One person owns the manuscript. They share it with the people they work with, and each of them opens it in their own MangaLoft. Before you draw, you check out what you will change: a layer, or a whole page. While you hold it, no one else can change it. When you are done you check it in, and everyone else gets your drawing when they Update.
When the manuscript is finished, the owner wraps it up: the work comes back into their own file, and the shared copy can be deleted.
Connecting with someone shares no manuscript. It only lets you invite each other later.
The pictures in these pages show Alice and Bob, each on a Mac. On iPad the steps are the same.