If they are already a Wordpress user on your network click the "Email" field.

Select the "Role" you want them to have (see more about roles further down on the page.

Subscriber
Contributor
Author
Editor
Administrator

Click "Add Existing User". If they aren't already a user on the network, you'll get an error message. If that happens, follow the steps for adding a new user.

To add a user who isn't already on your Wordpress network. Click the "Username (required)" field and enter a username for them.

Click the "Email (required)" field and enter their email address.

You can also set an expiration date for the user in that role. This may be appropriate for student access for a particular class offering.

You can pick an amount of time or a date for the expiration.

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

You can choose what you want to happen when the expiration times arrives. You can have the user's role change or their password change preventing them from logging in.

Click the "User Expired Notification" field.

Then you can select who will be notified when the expiration occurs. You can notify the user, the user and the administrator, just the administrator, or nobody.

Finally, click the "Add New User" button.

How to Add a New or Existing User in WordPress