Enter your client's email address and click Send Invitation. Use this tool to give read-only access to the reporting dashboard for this site. When you send an invitation, they will receive an e-mail inviting them to create an account. That account will only be able to view this one site. The user will not be able to change anything in the account or receive invoices.
You're all set! To manage Clients in the future, return to Manage -> Clients.