If you want to add a number of users in a group, you can import them from a csv file. See Importing Groups
Open the navigation menu and select Identity & Security. Under Identity, select Domains.
Click the name of the identity domain that you want to work in. You might need to change the compartment to find the domain that you want. Then, click Groups.
Select the group you want add users to.
Select Assign user to groups.
To add users to the group, select the checkbox for each user that you want to
add to the group.
Tip
To search for a
user, select the text box, enter all or part of the beginning of the
username, first name, or last name of the user, and then press
Enter.