Adding a contact is similar to sending invites and to do that:
Select your company profile then click on the Plus Icon followed by Contact.
On the popup page, put in the email address/es of the student or employee that you want to invite/add.
Select the language of the message, the role of the person, and on which group he or she belongs.

*Note: You can add the person you invited to a group later.
Click on Invite and an email will be sent.