You must add Interactive activities within a role lane in the process. When you try to add an Interactive activity outside a role lane, Studio prompts you for an already existing role or allows you to create a new one.
The role lane where you add the Interactive activity determines which users can access it. Only the users assigned to that role can run the Interactive activity.
There are no transitions to or from the Global Creation activity. There is an implied transition from the Global Creation to the Begin activity.