If the user you're sharing with has view-only access and you want to give them edit access, their user permissions need to be edited under Manage > Roles.
The user needs the following permissions:
- Assign Desk permission for the building/floor
- Desk Delegation permission
All users collaborating on the same draft will see the same queue and can work on it simultaneously.
Editors can lock a draft, restricting further edits from users with Collaborator access, and forcing users with Editor privileges to unlock a draft before it can be edited or published.