If you are on a premium plan (Professional or higher), you can add clients to individual websites. This way, clients can receive ChangeAlerts and log in and view their backups. Clients cannot delete websites or modify settings, but they are empowered to perform zip requests, on-demand backups, and restores.
Here's how to do it:
You can add clients on a per website basis by selecting the "settings" tab on menu after you have selected a particular website.
2. Client Settings
Clients will be able to only access the websites for which they were added.
For more information about these roles, check out this support article.