But Shared Goals can only be added for "Team" cohorts, not "Group" cohorts.
To learn how to add a team goal, read: Add Shared Goals for your Cohort
Did you create a group cohort and now need to switch it to a team cohort? Read this to learn how: How to change the cohort type? How to switch between Team & Group?
Don't know what type of cohort to create? Read: What is the difference between Group & Team cohort?