You might want to add a user to your service from the backend.
You can add individual users by following the steps below:
From the user section of the left menu, select Users > Manage User
Click the Add User button.
The fields marked * are mandatory and you need to fill in those details.
The options available under Advanced details are optional and You can fill in the information of these fields if you have them handy. There will be no issues if you choose not to fill these fields and left them empty.
Fill in the user details and click on the Submit button.
A profile for the user is created and you can check them under Manage users.
To upload users in bulk, please check the article: How to add users with CSV files.