WordPress comes with a built-in user management system. This lets you add users with different roles and permission levels.
1. Go to the "Users" plugin and click the "Add New".
2. Fill out the form to create a new user. Note that the username can’t be easily changed later! Use the ‘Generate password’ button to automatically create a strong password, and check the 'send new user email' to send them an email letting them know how to log in. This will also have a link, so they can set a different password if they want.
3. Once you are done, click the ‘Add New User’ button at the bottom of the screen.