You have to either create a group, give permissions to group and then add assign that group to user or create user and assign permissions to that user.
Add group Stuff-users
.
Under available permissions in Available Permissions
Select
YourApp | YourModel | Can add...
YourApp | YourModel | Can change...
YourApp | YourModel | Can Delete...
Then make sure you have clicked on the arrow pointing to Change Permissions. This will move the specific permission to Change Permissions.
Click Save.
Create or open Users. Select the user Stuff
Select Active and Staff Users.
Select Stuff-users
from Available Groups and click the arrow pointing to Chosen Groups. This will move the Support group to Chosen Group.
Don't make any change to User Permissions unless you want to grant additional permissions to any specific user.
Click save.
Have the user logout and log back in.