How to add & remove user group access to collections and set items locked
Once a collection has been created you need to give access to the correct user groups.
Open the collection you want to give access to and use the submenu to go to Access. From here you'll see an overview of all the groups that have access already, you can revoke access from here as well as add new user groups to the collection.
You can also go via the user group to see what content each group has access to
Access can be prevented on each item, this will show to users as locked.