This section is available for you when clicking on the left upper corner Menu and then navigating to Administration > Users.
To find out how to create a new User – take a look at this article.
Right after creating such a user you will have an option to assign him a role – either an Owner or a User (take a look what is the difference here). After picking a role you just click on Save button to submit changes.
To delete a given user you need to pick his surname from the list and then click Delete button on the right upper corner and confirm the deletion.