When adding a Client, you must also add a Contact for the Client. You can d this during the initial Client setup or by selecting Contacts from the sidebar.
You can have a number of Contacts for each Client. When you add a new contact they will receive an email notification that they have been added and a login url to access the client dashboard.
The Contact will have access to the client dashboard with their login and will be able to submit requests to via the dashboard.
They will also receive notifications by email for requests and task statuses, this can be turned off in the contact tab.